The botanic garden: a poem, in two parts. Part I. Containing the economy of vegetation. Part II. The loves of the plants. With philosophical notes.
IT VER, ET VENUS; ET VENERIS PRAENUNCIUS ANTEPENNATUS GRADITUR ZEPHYRUS VESTIGIA PROPTER;FLORA QUIBUS MATER, PRAESPERGENS ANTE VIAICUNCTA, COLORIBUS EGREGIIS ET ODORIBUS OPPLET.LUCRET.
THE general deſign of the following ſheets is to inliſt Imagination under the banner of Science; and to lead her votaries from the looſer analogies, which dreſs out the imagery of poetry, to the ſtricter, ones which form the ratiocination of philoſophy. While their particular deſign is to induce the ingenious to cultivate the knowledge of Botany, by introducing them to the veſtibule of that delightful ſcience, and recommending to their attention the immortal works of the celebrated Swediſh Naturaliſt, LINNEUS.
In the firſt Poem, or Economy of Vegetation, the phyſiology of Plants is delivered; and the operation of the Elements, as far as they may be ſuppoſed to affect the growth of Vegetables. In the ſecond Poem, or Loves of the Plants, the Sexual Syſtem of Linneus is explained, with the remarkable properties of many particular plants.
IT may be proper here to apologize for many of the ſubſequent conjectures on ſome articles of natural philoſophy, as not being ſupported by accurate inveſtigation or concluſive experiments. Extravagant theories however in thoſe parts of philoſophy, where our knowledge is yet imperfect, are not without their uſe; as they encourage the execution of laborious experiments, or the inveſtigation of ingeniouſ deductions, to confirm or refute them. And ſince natural objects are allied to each other by many affinities, every kind of theoretic diſtribution of them addſ to our knowledge by developing ſome of their analogies.
The Roſicrucian doctrine of Gnomes, Sylphs, Nymphs, and Salamanders, was thought to afford a proper machinery for a Botanic poem; as it is probable, that they were originally the names of hieroglyphic figures repreſenting the elements.
Many of the important operations of Nature were ſhadowed or allegorized in the heathen mythology, as the firſt Cupid ſpringing from the Egg of Night, the marriage of Cupid and Pſyche, the Rape of Proſerpine, the Congreſs of Jupiter and Juno, Death and Reſuſcitation of Adonis, &c. many of which are ingeniouſly explained in the works of Bacon, Vol. V. p. 47. 4th Edit. London, 1778. The [Page viii] Egyptians were poſſeſſed of many diſcoveries in philoſophy and chemiſtry before the invention of letters; theſe were then expreſſed in hieroglyphic paintings of men and animals; which after the diſcovery of the alphabet were deſcribed and animated by the poets, and became firſt the deities of Egypt, and afterwards of Greece and Rome. Alluſions to thoſe fables were therefore thought proper ornaments to a philoſophical poem, and are occaſionally introduced either as repreſented by the poets, or preſerved on the numerous gems and medallions of antiquity.
Repton, Nov. 28, 1788.
THE Genius of the place invites the Goddeſs of Botany. 1. She deſcends, is received by Spring, and the Elements, 59. Addreſſes the Nymphs of Fire. Star-light Night ſeen in the Camera Obſcura, 81. I. Love created the Univerſe. Chaos explodes. All the Stars revolve. God. 97. II. Shooting Stars. Lightning. Rainbow. Colours of the Morning and Evening Skies. Exterior Atmoſphere of inflammable Air. Twilight. Fire-balls. Aurora Borealis. Planets. Comets. Fixed Stars. Sun's Orb, 115. III. 1. Fires at the Earth's Centre. Animal Incubation, 137. 2. Volcanic Mountains. Venus viſits the Cyclops, 149. IV. Heat confined on the Earth by the Air. Phoſphoric lights in the Evening. Bolognian Stone. Calcined Shells. Memnon's Harp, 173. Ignis fatuus. Luminous Flowers. Glow-worm. Fire-fly. Luminous Sea-inſects. Electric Eel. Eagle armed with Lightning, 189. V. 1. Diſcovery of Fire. Meduſa, 209. 2. The chemical Properties of Fire. Phoſphorus. Lady in Love, 223. 3. Gun-powder, 237. VI. Steam-engine applied to Pumps, Bellows, Water-engines, Corn-mills, Coining, Barges, Waggons, Flying-chariots, 253. Labours of Hercules. Abyla and Calpe, 297. VII. 1. Electric Machine. Heſperian Dragon. Electric kiſs. Halo round the heads of Saints. Electric Shock. Fairy-rings, 335. 2. Death of Profeſſor Richman, 371. 3. Franklin draws Lightning [Page xii] from the Clouds. Cupid ſnatches the Thunder-bolt from Jupiter▪ 383. VIII. Phoſphoric Acid and Vital Heat produced in the Blood▪ The great Egg of Night, 399. IX. Weſtern Wind unfettered▪ Naiad releaſed. Froſt aſſailed. Whale attacked, 421. X. Buds and Flowers expanded by Warmth, Electricity, and Light. Drawings with colourleſs ſympathetic Inks; which appear when warmed by the Fire, 457. XI. Sirius. Jupiter and Semele. Northern Conſtellations. Ice-iſlands navigated into the Tropic Seas. Rainy Monſoons, 497. XII. Points erected to procure Rain. Elijah on Mount-Carmel, 547. Departure of the Nymphs of Fire like ſparks from artificial Fireworks, 585.
ADDRESS to the Gnomes. I. The Earth thrown from a volcano of the Sun; it's atmoſphere and ocean; it's journey through the zodiac; viciſſitude of day-light, and of ſeaſons, 11. II. Primeval iſlands. Paradiſe, or the golden Age. Venus riſing from the ſea, 33. III. The firſt great earthquakes; continents raiſed from the ſea; the Moon thrown from a volcano, has no atmoſphere, and is frozen; the earth's diurnal motion retarded; it's axis more inclined; whirls with the moon round a new centre. 67. IV. Formation of lime-ſtone by aqueous ſolution; calcaneous ſpar; white marble; antient ſtatue of Hercules reſting from his labours. Antinous. Apollo of Belvidere. Venus de Medici. Lady Elizabeth Foſter, and Lady Melbourn by Mrs. Damer. 93. V. 1. Of moraſſes. Whence the production of Salt by elutriation. Salt-mines at Cracow, 115. 2. Production of nitre. Mars and Venus caught by Vulcan, 143. 3. Production of iron. Mr. Michel's improvement of artificial magnets. Uſes of Steel in agriculture, navigation, war, 183. IV. Production of acids, whence Flint. Sea-ſand. Selenite. Aſbeſtus. Fluor. Onyx, Agate, Mocho, Opal, Sapphire, Ruby, Diamond. Jupiter and Europa, 215. VI. 1. New ſubterraneous fires from fermentation. Production of Clays; manufacture of Porcelain in China; in Italy; in England. Mr. Wedgwood's works at Etruria in Staffordſhire. Cameo of a Slave in Chains; of Hope. Figures on the Portland or Barberini vaſe explained, 271. 2. Coal; Pyrite; Naphtha; Jet; Amber. Dr. Franklin's diſcovery of diſarming the Tempeſt of it's lightning. Liberty of America; of Ireland; of France, 349. VII. Antient [Page 58] central ſubterraneous fires. Production of Tin, Copper, Zink, Lead, Mercury, Platina, Gold and Silver. Deſtruction of Mexico. Slavery of Africa, 395. VIII. Deſtruction of the armies of Cambyſes, 431. IX. Gnomes like ſtars of an Orrery. Inroads of the Sea ſtopped. Rocks cultivated. Hannibal paſſes the Alps, 499. X. Matter circulates. Manures to Vegetables like Chyle to Animals. Plants riſing from the Earth. St. Peter delivered from Priſon, 537. Departure of the Gnomes, 575.
ADDRESS to the Nymphs. I. Steam riſes from the ocean, floats in clouds, deſcends in rain and dew, or is condenſed on hills, produces ſprings, and rivers, and returns to the ſea. So the blood circulates through the body and returns to the heart. 11. II. 1. Tides, 57. 2. Echinus, nautilus, pinna, cancer. Grotto of a mermaid. 65. 3. Oil ſtills the waves. Coral rocks. Ship-worm, or Teredo. Maelſtrome, a whirlpool on the coaſt of Norway. 85. III. Rivers from beneath the ſnows on the Alps. The Tibber. 103. IV. Overflowing of the Nile from African Monſoons, 129. V. 1. Gieſar, a boiling fountain in Iceland, deſtroyed by inundation, and conſequent earthquake, 145. 2. Warm medicinal ſprings. Buxton. Duke and Dutcheſs of Devonſhire. 157. VI. Combination of vital air and inflammable gas produces water. Which is another ſource of ſprings and rivers. Allegorical loves of Jupiter and Juno productive of vernal ſhowers. 201. VII. Aquatic Taſte. Diſtant murmur of the ſea by night. Sea-horſe. Nereid ſinging. 261. VIII. The Nymphs of the river Derwent lament the death of Mrs. French, 297. IX. Inland navigation. Monument for Mr. Brindley, 321. X. Pumps explained. Child ſucking. Mothers exhorted to nurſe their children. Cherub ſleeping. 345. XI. Engines for extinguiſhing fire. Story of two lovers periſhing in the flames. 377. XII. Charities of Miſs Jones, 427. [Page 112] XIII. Marſhes drained. Hercules conquers Achilous. The horn of Plenty. 463. XIV. Showers. Dews. Floating lands with water. Lacteal ſyſtem in animals. Caravan drinking. 509. Departure of the Nymphs like water ſpiders; like northern nations ſkaiting on the ice. 549.
ADDRESS to the Sylphs. I. Trade-winds. Monſoons. N. E. and S. W. winds. Land and ſea breezes. Irregular winds. 9. II. Production of vital air from oxygene and light. The marriage of Cupid and Pſyche. 25. III. 1. Syroc. Simoom. Tornado. 63. 2. Fog. Contagion. Story of Thyrſis and Aegle. Love and Death. 79. IV. 1. Barometer. Air-pump. 127. 2. Air-balloon of Mongulfier. Death of Rozier. Icarus. 143. V. Diſcoveries of Dr. Prieſtley. Evolutions and combinations of pure air. Rape of Proſerpine. 165. VI. Sea-balloons, or houſes conſtructed to move under the ſea. Death of Mr. Day. Of Mr. Spalding. Of Captain Pierce and his Daughters. 195. VII. Sylphs of muſic. Cecelia ſinging. Cupid with a lyre riding upon a lion. 233. VIII. Deſtruction of Senacherib's army by a peſtilential wind. Shadow of Death. 263. IX. 1. Wiſh to poſſeſs the ſecret of changing the courſe of the winds. 305. 2. Monſter devouring air ſubdued by Mr. Kirwan. 321. X. 1. Seeds ſuſpended in their pods. Stars diſcovered by Mr. Herſchel. Deſtruction and reſuſcitation of all things. 351. 2. Seeds within ſeeds, and bulbs within bulbs. Picture on the retina of the eye. Concentric ſtrata of the earth. The great ſeed. 381. 3. The root, pith, lobes, plume, calyx, coral, ſap, blood, leaves reſpire and abſorb light. The crocodile in its egg. 409. XI. Opening [Page 160] of the flower. The petals, ſtyle, anthers, prolific duſt. Tranſmutation of the ſilkworm. 441. XII. 1. Leaf-buds changed into flower-buds by wounding the bark, or ſtrangulating a part of the branch. 461. 2. Ingrafting. Aaron's rod pullulates. 477. XIII. 1. Inſects on trees. Humming-bird alarmed by the ſpiderlike apearance of Cyprepedia. 491. 2. Diſeaſes of vegetables. Scratch on unnealed glaſs. 511. XIV. 1. Tender flowers. Amaryllis, fritillary, erythrina, mimoſa, cerea. 523. 2. Vines. Oranges. Diana's trees. Kew garden. The royal family. 541. XV. Offering to Hygeia. 587. Departure of the Goddeſs. 615.
- ROSICRUSIAN machinery. 73
- All bodies are immerſed in the matter of heat. Particles of bodies do not touch each other. 97
- Gradual progreſs of the formation of the earth, and of plants and animals. Monſtrous births 101
- Fixed stars approach towards each other, they were projected from chaos by exploſion, and the planets projected from them 105
- An atmoſphere of inflammable air above the common atmoſphere principally about the poles 123
- Twilight fifty miles high. Wants further obſervations 126
- Immediate cauſe of volcanos from ſteam and other vapours. They prevent greater earthquakes 152
- Conductors of heat. Cold on the tops of mountains 174
- Phoſphoreſcent light in the evening from all bodies 177
- Phoſphoric light from calcined ſhells. Bolognian ſtone. Experiments of Beccari and Wilſon 182
- Ignis fatuus doubtful 189
- Electric Eel. Its electric organs. Compared to the electric Leyden phial 202
- Diſcovery of fire. Tools of ſteel. Foreſts ſubdued. Quantity of food increaſed by cookery 212
- Meduſa originally an hieroglyphic of divine wiſdom 218
- Cauſe of exploſions from combined heat. Heat given out from air in reſpiration. Oxygene looſes leſs heat when converted into nitrous acid than in any other of its combinations 226
- Sparks from the colliſion of flints are electric. From the colliſion of flint and ſteel are from the combuſtion of the steel 229
- Gunpowder deſcribed by Bacon. Its power. Should be lighted in the centre. A new kind of it. Levels the weak and strong 242
- Steam-engine invented by Savery. Improved by Newcomen. Perfected by Watt and Boulton 254
- Divine benevolence. The parts of nature not of equal excellence 278
- Mr. Boulton's ſteam-engine for the purpoſe of coining would ſave many lives from the executioner 281
- Labours of Hercules of great antiquity. Pillars of Hercules. Surface of the Mediteranean lower than the Atlantic. Abyla and Calpe. Flood of Deucalion 297
- Accumulation of electricity not from friction 335
- Mr. Bennet's ſenſible electrometer 345
- Halo of saints is pictorial language 358
- We have a senſe adapted to perceive heat but not electricity 365
- Paralytic limbs move by electric influence 367
- Death of Profeſſor Richman by electricity 373
- Lightning drawn from the clouds. How to be ſafe in thunder storms 383
- Animal heat from air in reſpiration. Perpetual neceſſity of reſpiration. Spirit of animation perpetually renewed 401
- Cupid riſes from the egg of night. Mrs. Coſway's painting of this ſubject 413
- Weſtern-winds. Their origin. Warmer than ſouth-winds. Produce a thaw 430
- Water expands in freezing. Deſtroys ſucculent plants, not reſinous ones. Trees in valleys more liable to injury. Fig-trees bent to the ground in winter 439
- Buds and bulbs are the winter cradle of the plant. Defended from froſt and from inſects. Tulip produces one flower-bulb and several leaf-bulbs, and periſhes. 460
- [Page 212] Electricity forwards the growth of plants. Silk-worms electriſed ſpin ſooner. Water decompoſed in vegetables, and by electricity 463
- Matter of heat if different from light. Vegetables blanched by excluſion of light. Turn tht upper ſurface of their leaves to the light. Water decompoſed as it eſcapes from their pores. Hence vegetables purify air in the day time only. 462
- Sympathetic inks which appear by heat, and diſappear in the cold. Made from cobalt 487
- Star in Caſſiope's chair 515
- Ice-iſlands 100 fathoms deep. Sea-ice more difficult of ſolution. Ice evaporates producing great cold. Ice-iſlands increaſe. Should be navigated into ſouthern climates. Some ice-iſlands have floated ſouthwards 60 miles long. Steam attending them in warm climates 529
- Monſoon cools the ſands of Abyſſinia 545
- Aſcending vapours are electriſed plus, as appears from an experiment of Mr. Bennet. Electricity ſupports vapour in clouds. Thunder ſhowers from combination of inflammable and vital airs 551
- Solar volcanos analogous to terreſtrial and lunar ones. Spots of the ſun are excavations 14
- Spherical form of the earth. Ocean from condenſed vapour. Character of Mr. Whitehurſt 17
- Granite the oldeſt part of the earth. Then limeſtone. And laſtly, clay, iron, coal, ſandſtone. Three great concentric diviſions of the globe 35
- Formation of primeval iſlands before the production of the moon. Paradiſe. The Golden Age. Rain-bow. Water of the ſea originally freſh 36
- Venus riſing from the ſea an hieroglyphic emblem of the production of the earth beneath the ocean 47
- Firſt great volcanos in the central parts of the earth. From steam, inflammable gas, and vital air. Preſent volcanos like mole-hills 66
- Moon has little or no atmoſphere. Its ocean is frozen. Is not yet inhabited, but may be in time 80
- Earth's axis changed by the aſcent of the moon. Its diurnal motion retarded. One great tide 82
- Limeſtone produced from ſhells. Spars with double refractions. Marble. Chalk 91
- Antient ſtatues of Hercules. Antinous. Apollo. Venus. Deſigns of Roubiliac. Monument of General Wade. Statues of Mrs. Damer 99
- Moraſſes reſt on limeſtone. Of immenſe extent 114
- Salts from animal and vegetable bodies decompoſe each other, except marine ſalt. Salt mines in Poland. Timber does not decay in them. Rock-ſalt produced by evaporation from ſea-water. Foſſil ſhells in ſalt mines. Salt in hollow pyramids. In cubes. Sea-water contains about one-thirtieth of salt 117
- Nitre, native in Bengal and Italy. Nitrous gas combined with vital air produces red clouds, and the two airs occupy leſs space than one of them before, and give out heat. Oxygene and azote produce nitrous acid 141
- Iron from decompoſed vegetables. Chalybeat springs. Fern-leaves in nodules of iron Concentric ſpheres of iron nodules owing to polarity, like iron-filings arranged by a magnet. Great ſtrata of the earth owing to their polarity 181
- Hardneſs of ſteel for tools. Gave ſuperiority to the European nations. Welding of ſteel. Its magnetiſm. Uſes of gold 190
- Artificial magnets improved by Savery and Dr. Knight, perfected by Mr. Michel. How produced. Polarity owing to the earth's rotatory motion. The electric fluid, and the matter of heat, and magnetiſm gravitate on each other. Magnetiſm being the lighteſt is found neareſt the axis of the motion. Electricity produces northern lights by its centrifugal motion 193
- Acids from vegetable recrements. Flint has its acid from the new world. Its baſe in part from the old world, and in part from the new. Precious ſtones 213
- Diamond. Its great refraction of light. Its volatibility by heat. If an inflammable body. 226
- Fires of the new world from fermentation. Whence ſulphur and bitumen by ſublimation, the clay, coal, and flint remaining 273
- Colours not diſtinguiſhable in the enamelkiln, till a bit of dry wood Is introduced 281
- Etrurian pottery prior to the foundations of Rome. Excelled in fine forms, and in a non-vitreous encauſtic painting, which was loſt till reſtored by Mr. Wedgwood. Still influences the taſte of the inhabitants 289
- Mr. Wedgwood's cameo of a ſlave in chains, and of Hope 313
- Baſſo-relievos of two or more colours not made by the antients. Invented by Mr. Wedgwood 340
- [Page 213] Petroleum and naptha have been ſublimed. Whence jet and amber. They abſorb air. Attract ſtraws when rubbed. Electricity from electron the greek name for amber 351
- Clefts in granite rocks in which metals are found. Iron and manganeſe found in all vegetables. Manganeſe in limeſtone. Warm ſprings from ſteam riſing up the clefts of granite and limeſtone. Ponderous earth in limeſtone clefts and in granite. Copper, lead, iron, from deſcending materials. High mountains of granite contain no ores near their summits. Tranſmutation of metals. Of lead into calamy. Into ſilver 394
- Armies of Cambyſes deſtroyed by famine, and by ſand-ſtorms 431
- Whirling turrets of ſand deſcribed and explained 474
- Granite ſhews iron as it decompoſes. Marble decompoſes. Immenſe quantity of charcoal exiſts in limeſtone. Volcanic ſlags decompoſe, and become clay 519
- Millſtones raiſed by wooden pegs 520
- Hannibal made a paſſage by fire over the Alps 527
- Paſſed tenſe of many words twofold, as driven or drove, ſpoken or spoke. A poetic licence 575
- Clouds conſiſt of aqueous ſpheres, which do not eaſily unite, like globules of quickſilver, as may be ſeen in riding through water. Owing to electricity. Snow. Hailſtones rounded by attrition and diſſolution of their angles. Not from frozen drops of water 15
- Dew on points and edges of graſs, or hangs over cabbage-leaves, needle floats on water 18
- Miſts over rivers and on mountains. Halo round the moon. Shadow of a church-ſteeple upon a miſt. Dry miſt, or want of tranſparency of the air, a ſign of fair-weather 20
- Tides on both sides of the earth. Moon's tides ſhould be much greater than the earth's tides. The ocean of the moon is frozen 61
- Spiral form of ſhells ſaves calcareous matter. Serves them as an organ of hearing. Calcareous matter produced from inflamed membranes. Colours of ſhells, labradore-ſtone from mother-pearl. Foſſil ſhells not now found recent 66
- Sea-inſects like flowers. Actinia 82
- Production of pearls, not a diſeaſe of the fiſh. Crab's eyes. Reſervoirs of pearly matter 84
- Rocks of coral in the ſouth-ſea. Coralloid limeſtone at Linſel, and Coalbrook Dale 90
- Rocks thrown from mountains, ice from glaciers, and portions of earth, or moraſſes, removed by columns of water. Earth-motion in Shropſhire. Water of wells riſing above the level of the ground. St. Alkmond's well near Derby might be raiſed many yards, ſo as to ſerve the town. Well at Sheerneſs, and at Hartford in Connecticut 116
- Moonſoons attended with rain. Overflowing of the Nile. Vortex of aſcending air. Riſing of the Dogſtar announces the floods of the Nile. Anubis hung out upon their temples 129
- Situations exempt from rain. At the Line in Lower Egypt. On the coaſt of Peru 138
- Gieſar, a boiling fountain in Iceland. Water with great degrees of heat diſſolves ſiliceous matter. Earthquake from ſteam 150
- Warm ſprings not from decompoſed pyrites. From ſteam riſing up fiſſures from great depths 166
- Buxton bath poſſeſſes 82 degrees of heat. Is improperly called a warm bath. A chill at immerſion, and then a ſenſation of warmth, like the eye in an obſcure room owing to increaſed ſenſibility of the skin 184
- Water compounded of pure air and inflammable air with as much matter of heat as preserves it fluid. Perpetually decompoſed by vegetables in the ſun's light, and recompoſed in the atmoſphere 204
- Mythological interpretation of Jupiter and Juno deſigned as an emblem of the compoſition of water from two airs 260
- Death of Mrs. French 308
- Tomb of Mr. Brindley 321
- Invention of the pump. The piſton lifts the atmoſphere above it. The ſurrounding atmoſphere preſſes up the water into the vacuum. Manner in which a child ſucks 346
- Air-cell in engines for extinguiſhing fire. Water diſperſed by the exploſion of Gunpowder. Houſes preſerved from fire by earth on the floors, by a ſecond cieling of iron-plates or coarſe mortar. Wood impregnated with alabaſter or flint 386
- Muſcular actions and ſenſations of plants 440
- River Achelous. Horn of Plenty 475
- Flooding lands defends them from vernal froſts. Some ſprings depoſit calcareous earth. Some contain azotic gas, which contributes to produce nitre. Snow water leſs serviceable 520
- Cacalia produces much honey, that a part may be taken by inſects without injury 2
- Analyſis of common air. Source of azote. Of Oxygene. Water decompoſed by vegetable pores and the ſun's light. Blood gives out phlogiſton and receives vital air. Acquires heat and the vivifying principle 34
- Cupid and Pſyche 48
- Simoom, a peſtilential wind. Deſcribed. Owing to volcanic electricity. Not a whirlwind 65
- Contagion either animal or vegetable 85
- Thyrſis eſcapes the Plague 91
- Barometer and air-pump. Dew on exhauſting the receiver though the hygrometer points to dryneſs. Rare air will diſſolve or acquire more heat, and more moiſture, and more electricity 128
- Sound propagated beſt by denſe bodies, as wood, and water, and earth. Fiſh in ſpiral ſhells all ear 164
- Diſcoveries of Dr. Prieſtley. Green vegetable matter. Pure air contained in the calces of metals, as minium, manganeſe, calamy, ochre 166
- Fable of Proſerpine an antient chemical emblem 178
- Diving balloons ſupplied with pure air from minium. Account of one by Mr. Boyle 195
- Mr. Day. Mr. Spalding 217
- Captain Pierce and his daughters 219
- Peſtilential winds of volcanic origin. Jordan flows through a country of volcanos 274
- Change of wind owing to ſmall cauſes. If the wind could be governed, the products of the earth would be doubled, and its number of inhabitants increaſed 308
- Mr. Kirwan's treatiſe on temperature of climates 342
- Seeds of plants. Spawn of fiſh. Nutriment lodged in ſeeds. Their preſervation in their ſeed-veſſels 355
- Fixed stars approach each other 369
- Fable of the Phoenix 377
- Plants viſible within bulbs, and buds, and ſeeds 383
- Great Egg of Night 406
- Seeds ſhoot into the ground. Pith. Seed-lobes. Starch converted into ſugar. Like animal chyle 411
- Light occaſions the actions of vegetable muſcles. Keeps them awake 422
- Vegetable love in Parnaſſia, Nigella. Vegetable adultery in Collinſonia 456
- Strong vegetable ſhoots and roots bound with wire, in part debarked, whence leaf-buds converted into flower-buds. Theory of this curious fact 463
- Branches bent to the horizon bear more fruit 466
- Engrafting of a ſpotted paſſion-flower produced ſpots upon the ſtock. Apple ſoft on one side and hard on the other 479
- Cyprepedium aſſumes the form of a large ſpider to affright the humming-bird. Flyophris. Willow-wren ſucks the honey of the crown-imperial 513
- Diſeaſes of plants four kinds. Honey-dew 519
- Ergot a diſeaſe of rye 521
- Glaſs unannealed. Its cracks owing to elaſticity. One kind of lead-ore cracks into pieces. Prince Rupert's drops. Elaſtic balls 527
- Sleep of plants. Their irritability, ſenſibility, and voluntary motions 546
Etherial Forms! you chaſe the ſhooting ſtars,Or yoke the vollied lightnings to your cars.CANTO I. 1. 115.
THERE ſeem to be three concentric ſtrata of our incumbent atmoſphere; in which, or between them, are produced four kinds of meteors; lightning, ſhooting ſtars, fire-balls, and northern lights. Firſt, the lower region of air, or that which is denſe enough to reſiſt by the adheſion of its particles the deſcent of condenſed vapour, or clouds, which may extend from one to three or four miles high. In this region the common lightning is produced from the accumulation or defect of electric matter in thoſe floating fields of vapour either in reſpect to each other, or in reſpect to the earth beneath them, or the diſſolved vapour above them, which is conſtantly varying both with the change of the form of the clouds, which thus evolve a greater or leſs ſurface; and alſo with their ever-changing degree of condenſation. As the lightning is thus produced in denſe air, it proceeds but a ſhort courſe on account of the greater reſiſtance which it encounters, is attended with a loud exploſion, and appears with a red light.
2. The ſecond region of the atmoſphere I ſuppoſe to be that which has too little tenacity to ſupport condenſed vapour or clouds; but which yet contains inviſible vapour, or water in aerial ſolution. This aerial ſolution of water differs from that diſſolved in the matter of heat, as it is supported by its adheſion to the particles of air, and is not precipitated by cold. In this ſtratum it ſeems probable that the meteors called ſhooting ſtars are produced; and that they conſiſt of electric ſparks, or lightning, paſſing from one region to another of theſe inviſible fields of aero-aqueous ſolution. The height of theſe ſhooting ſtars has not yet been aſcertained by ſufficient obſervation; Dr. Blagden thinks their ſituation is lower down in the atmoſphere than that of fireballs, which he conjectures from their ſwift apparent motion, and aſcribes their ſmallneſs to the more minute diviſion of the electric matter of which they are suppoſed to conſiſt, owing to [Page 2] the geater reſiſtance of the denſer medium through which they paſs, than that in which the fire-balls exiſt. Mr. Brydone obſerved that the shooting stars appeared to him to be as high in the atmoſphere, when he was near the summit of mount Etna, as they do when obſerved from the plain. Phil. Tran. Vol. LXIII.
As the stratum of air, in which shooting stars are suppoſed to exiſt is much rarer than that in which lightning reſides, and yet much denſer than that in which fireballs are produced, they will be attracted at a greater diſtance than the former, and at a leſs than the latter. From this rarity of the air so small a sound will be produced by their exploſion, as not to reach the lower parts of the atmoſphere; their quantity of light from their greater diſtance being small, is never seen through denſe air at all, and thence does not appear red, like lightning or fire balls. There are no apparent clouds to emit or to attract them, becauſe the conſtituent parts of theſe aero-aqueous regions may poſſeſs an abundance or deficiency of electric matter and yet be in perfect reciprocal solution. And laſtly their apparent train of light is probably owing only to a continuance of their impreſſion on the eye; as when a fire-stick is whirled in the dark it gives the appearance of a compleat circle of fire: for theſe white trains of shooting stars quickly vaniſh, and do not seem to set any thing on fire in their paſſage, as seems to happen in the tranſit of fire-balls.
3. The second region or stratum of air terminates I suppoſe where the twilight ceaſes to be refracted, that is, where the air is 3000 times rarer than at the surface of the earth; and where it seems probable that the common air ends, and is ſurrounded by an atmoſphere of inflammable gas tenfold rarer than itſelf. In this region I believe fire-balls ſometimes to paſs, and at other times the northern lights to exiſt. One of theſe fire-balls or draco volans, was obſerved by Dr. Pringle and many others on Nov. 26, 1758, which was afterwards eſtimated to have been a mile and a half in circumference, to have been about one hundred miles high, and to have moved towards the north with a velocity of near thirty miles in a ſecond of time. This meteor had a real tail many miles long, which threw off ſparks in its courſe, and the whole exploded with a sound like diſtant thunder. Philoſ. Tranſ. Vol. LI.
Dr. Blagden has related the hiſtory of another large meteor, or fire-ball, which was ſeen the 18th of Auguſt, 1783, with many ingenious obſervations and conjectures. This was eſtimated to be between 60 and 70 miles high, and to travel 1000 miles at the rate of about twenty miles in a ſecond. This fire-ball had likewiſe a real train of light left behind it in its paſſage, which varied in colour; and in ſome part of its courſe gave off ſparks or exploſions where it had been brighteſt; and a duſky red streak remained viſible perhaps a minute. Philoſ. Tranſ. Vol. LXXIV.
Theſe fire-balls differ from lightning, and from ſhooting ſtars in many remarkable circumſtances; as their very great bulk, being a mile and a half in diameter; their travelling 1000 miles nearly horizontally; their throwing off sparks in their paſſage; and changing colours from bright blue to duſky red; and leaving a train of fire behind them, continuing about a minute. They differ from the northern lights in not being diffuſed, but paſſing from one point of the heavens to another in a defined line; and this in a region above the crepuſcular atmoſphere, where the air is 3000 times rarer than at the [Page 3] ſurface of the earth. There has not yet been even a conjecture which can account for theſe appearances!—One I ſhall therefore hazard; which, if it does not inform, may amuſe the reader.
In the note on l. 123, it was ſhewn that there is probably a ſupernatant ſtratum of inflammable gas or hydrogene, over the common atmoſphere; and whoſe denſity at the ſurface where they meet, muſt be at leaſt ten times leſs than that upon which it ſwims; like chemical ether floating upon water, and perhaps without any real contact. 1. In this region, where the aerial atmoſphere terminates and the inflammable one begins, the quantity of tenacity or reſiſtance muſt be almoſt inconceivable; in which a ball of electricity might paſs 1000 miles with greater eaſe than through a thouſandth part of an inch of glaſs. 2. Such a ball of electricity paſſing between inflammable and common air would ſet fire to them in a line as it paſſed along; which would differ in colour according to the greater proportionate commixture of the two airs; and from the same cauſe there might occur greater degrees of inflammation, or branches of fire, in ſome parts of its courſe.
As theſe fire-balls travel in a defined line, it is pretty evident from the known laws of electricity, that they muſt be attracted; and as they are a mile or more in diameter, they muſt be emitted from a large ſurface of electric matter; becauſe large nobs give larger ſparks, leſs diffuſed, and more brightly luminous, than leſs ones or points, and reſiſt more forceably the emiſſion of the electric matter. What is there in nature can attract them at ſo great a diſtance as 1000 miles, and so forceably as to detach an electric ſpark of a mile diameter? Can volcanos at the time of their eruptions have this effect, as they are generally attended with lightning? Future obſervations muſt diſcover theſe ſecret operations of nature! As a stream of common air is carried along with the paſſage of electric aura from one body to another; it is eaſy to conceive, that the common air and the inflammable air between which the fire-ball is ſuppoſed to paſs, will be partially intermixed by being thus agitated, and ſo far as it becomes intermixed it will take fire, and produce the linear flame and branching ſparks above deſcribed. In this circumſtance of their being attracted, and thence paſſing in a defined line, the fire-balls ſeem to differ from the coruſcations of the aurora borealis, or northern lights, which probably take place in the ſame region of the atmoſphere; where the common air exiſts in extreme tenuity, and is covered by a ſtill rarer ſphere of inflammable gas, ten times lighter than itſelf.
As the electric ſtreams, which conſtitute theſe northern lights, ſeem to be repelled or radiated from an accumulation of that fluid in the north, and not attracted like the fireballs; this accounts for the diffuſion of their light, as well as the ſilence of their paſſage; while their variety of colours, and the permanency of them, and even the breadth of them in different places, may depend on their ſetting on fire the mixture of inflammable and common air through which they paſs; as ſeems to happen in the tranſit of the fire-balls.
[Page 4] It was obſerved by Dr. Prieſtley that the electric ſhock taken through inflammable air was red, in common air it is blueiſh; to theſe circumſtances perhaps ſome of the colours of the northern lights may bear analogy; though the denſity of the medium through which light is ſeen muſt principally vary its colour, as is well explained by Mr. Morgan. Phil. Tranſ. Vol. LXXV. Hence lightning is red when ſeen through a dark cloud, or near the horizon; becauſe the more refrangible rays cannot permeate so denſe a medium. But the ſhooting ſtars conſiſt of white light, as they are generally ſeen on clear nights, and nearly vertical: in other ſituations their light is probably too faint to come to us. But as in ſome remarkable appearances of the northern lights, as in March, 1716, all the priſmatic colours were ſeen quickly to ſucceed each other, theſe appear to have been owing to real combuſtion; as the denſity of the interpoſed medium could not be ſuppoſed to change ſo frequently; and therefore theſe colours muſt have been owing to different degrees of heat according to Mr. Morgan's theory of combuſtion. In Smith's Optics, p. 69. the priſmatic colours, and optical deceptions of the northern lights are deſcribed by Mr. Cotes.
The Torricellian vacuum, if perfectly free from air, is ſaid by Mr. Morgan and others to be a perfect non-conductor. This circumſtance therefore would preclude the electric ſtreams from riſing above the atmoſphere. But as Mr. Morgan did not try to paſs an electric ſhock through a vacuum, and as air, or ſomething containing air, surrounding the tranſit of electricity may be neceſſary to the production of light, the concluſion may perhaps still be dubious. If however the streams of the northern lights were suppoſed to riſe above our atmoſphere, they would only be viſible at each extremity of their courſe; where they emerge from, or are again immerged into the atmoſphere; but not in their journey through the vacuum; for the abſence of electric light in a vacuum is ſufficiently proved by the common experiment of ſhaking a barometer in the dark; the electricity, produced by the friction of the mercury in the glaſs at its top, is luminous if the barometer has a little air in it; but there is no light if the vacuum be complete.
The aurora borealis, or northern dawn, is very ingeniouſly accounted for by Dr. Franklin on principles of electricity. He premiſes the following electric phenomena: 1. that all new fallen snow has much poſitive electricity standing on its ſurface. 2. That about twelve degrees of latitude round the poles are covered with a cruſt of eternal ice, which is impervious to the electric fluid. 3. That the denſe part of the atmoſphere riſes but a few miles high; and that in the rarer parts of it the electric fluid will paſs to almoſt any diſtance.
Hence he suppoſes there muſt be a great accumulation of poſitive electric matter on the freſh fallen ſnow in the polar regions; which, not being able to paſs through the cruſt of ice into the earth, muſt riſe into the rare air of the upper parts of our atmoſphere, which will the leaſt reſiſt its paſſage; and paſſing towards the equator deſcend again into the denſer atmoſphere, and thence into the earth in silent streams. And that many of the appearances attending theſe lights are optical deceptions, owing to the situation of the eye that beholds them; which makes all aſcending parallel lines appear to converge to a point.
[Page 5] The idea, above explained in note on l. 123, of the exiſtence of a sphere of inflammable gas over the aerial atmoſphere would much favour this theory of Dr. Franklin; becauſe in that caſe the denſe aerial atmoſphere would riſe a much leſs height in the polar regions, diminiſhing almoſt to nothing at the pole itſelf; and thus give an eaſier paſſage to the aſcent of the electric fluid. And from the great difference in the ſpecific gravity of the two airs, and the velocity of the earth's rotation, there muſt be a place between the poles and the equator, where the superior atmoſphere of inflammable gas would terminate; which would account for theſe ſtreams of the aurora borealis not appearing near the equator; add to this that it is probable the electric fluid may be heavier than the magnetic one; and will thence by the rotation of the earth's surface aſcend over the magnetic one by its centrifugal force; and may thus be induced to riſe through the thin ſtratum of aerial atmoſphere over the poles. See note on Canto II. l. 193. I ſhall have occaſion again to mention this great accumulation of inflammable air over the poles; and to conjecture that theſe northern lights may be produced by the union of inflammable with common air, without the aſſiſtance of the electric ſpark to throw them into combuſtion.
The antiquity of the appearance of northern lights has been doubted; as none were recorded in our annals ſince the remarkable one on Nov. 14, 1574, till another remarkable one on March 6, 1716, and the three following nights, which were ſeen at the same time in Ireland, Ruſſia, and Poland, extending near 30 degrees of longitude and from about the 50th degree of latitude over almoſt all the north of Europe. There is however reaſon to believe them of remote antiquity though inaccurately deſcribed; thus the following curious paſſage from the Book of Maccabees, (B. II. c. v.) is ſuch a deſcription of them, as might probably be given by an ignorant and alarmed people. ‘Through all the city, for the ſpace of almoſt forty days, there were ſeen horſemen running in the air, in cloth of gold, and armed with lances, like a band of ſoldiers; and troops of horſemen in array encountering and running one againſt another, with ſhaking of ſhields and multitude of pikes, and drawing of ſwords, and caſting of darts, and glittering of golden ornaments and harneſs.’
Cling round the aerial bow with priſms bright,And pleaſed untwiſt the ſevenfold threads of light.CANTO I. l. 117.
THE manner in which the rainbow is produced was in some meaſure underſtood before Sir Iſaac Newton had diſcovered his theory of colours. The firſt perſon who expreſſly ſhewed the rainbow to be formed by the reflection of the sunbeams from drops of falling rain was Antonio de Dominis. This was afterwards more fully and diſtinctly explained by Des Cartes. But what cauſed the diverſity of its colours was not then underſtood; it was reſerved for the immortal Newton to diſcover that the rays of light consiſted of ſeven combined colours of different refrangibility, which could be ſeperated at pleaſure by a wedge of glaſs. Pemberton's View of Newton.
Sir Iſaac Newton diſcovered that the priſmatic ſpectrum was compoſed of ſeven colours in the following proportions, violet 80, indigo 40, blue 60, green 60, yellow 48, orange 27, red 45. If all theſe colours be painted on a circular card in the proportions above mentioned, and the card be rapidly whirled on its center, they produce in the eye the ſenſation of white. And any one of theſe colours may be imitated by painting a card with the two colours which are contiguous to it, in the ſame proportions as in the ſpectrum, and whirling them in the ſame manner.
3. If any four succeſſive colours in the priſmatic ſpectrum be mixed, a tint similar to a mixture of the ſecond and third colours will be produced, but not preciſely the ſame, becauſe they are not in the ſame proportion.
4. If beginning with any colour in the circular ſpectrum, you take of the ſecond colour a quantity equal to the firſt, second, and third; and add to that the fifth colour, equal in quantity to the fourth, fifth, and ſixth; and with theſe combine the ſeventh colour in the proportion it exiſts in the ſpectrum, white will be produced. Becauſe the firſt, ſecond, and third, compoſe only the ſecond; and the fourth, fifth, and ſixth, compoſe only the fifth; therefore if the ſeventh be added, the ſame effect is produced, as if all the ſeven were employed.
5. Beginning with any colour in the circular ſpectrum, if you take a tint compoſed of a certain proportion of the ſecond and third, (equal in quantity to the firſt, ſecond, third, and fourth,) and add to this the ſixth colour equal in quantity to the fifth, ſixth, and ſeventh, white will be produced.
[Page 7] From theſe curious experiments of Mr. Galton many phenomena in the chemical changes of colours may probably become better underſtood; eſpecially if, as I ſuppoſe, the ſame theory muſt apply to tranſmitted colours, as to reflected ones. Thus it is well known, that if the glaſs of mangoneſe, which is a tint probably compoſed of violet and indigo, be mixed in a certain proportion with the glaſs of lead, which is yellow; that the mixture becomes tranſparent. Now from Mr. Galton's experiments it appears, that in reflected colours such a mixture would produce white, that is, the same as if all the colours were reflected. And therefore in tranſmitted colours the ſame circumſtances muſt produce tranſparency, that is, the same as if all the colours were tranſmitted. For the particles, which conſtitute the glaſs of mangoneſe will tranſmit red, violet, indigo, and blue; and thoſe of the glaſs of lead will tranſmit orange, yellow, and green; hence all the primary colours by a mixture of theſe glaſſes become tranſmitted, that is, the glaſs becomes tranſparent.
Mr. Galton has further obſerved that five succeſſive priſmatic colours may be combined in ſuch proportions as to produce but one colour, a circumſtance which might be of conſequence in the art of painting. For if you begin at any part of the circular spectrum above deſcribed, and take the firſt, second, and third colours in the proportions in which they exiſt in the ſpectrum; theſe will compoſe only the ſecond colour equal in quantity to the firſt, ſecond, and third; add to theſe the third, fourth, and fifth in the proportion they exiſt in the ſpectrum, and theſe will produce the fourth colour equal in quantity to the third, fourth, and fifth. Conſequently this is preciſely the ſame thing, as mixing the ſecond and fourth colours only; which mixture would only produce the third colour. Therefore if you combine the firſt, ſecond, fourth, and fifth in the proportions in which they exiſt in the ſpectrum, with double the quantity of the third colour, this third colour will be produced. It is probable that many of the unexpected changes in mixing colours on a painter's eaſle, as well as in more fluid chemical mixtures, may depend on theſe principles rather than on a new arrangement or combination of their minute particles.
Mr. Galton further obſerves, that white may univerſally be produced by the combination of one priſmatic colour, and a tint intermediate to two others. Which tint may be diſtinguiſhed by a name compounded of the two colours, to which it is intermediate. Thus white is produced by a mixture of red with blue-green. Of orange with indigoblue. Of Yellow with violet-indigo. Of green with red-violet. Of blue with Orange-red. Of indigo with yellow-orange. Of violet with green-yellow. Which he further remarks exactly coincides with the theory and facts mentioned by Dr. Robert Darwin of Shrewſbury in his account of ocular ſpectra; who has ſhewn that when one of theſe contraſted colours has been long viewed, a ſpectrum or appearance of the other becomes viſible in the fatigued eye. Philoſ. Tranſ. Vol. LXXVI. for the year 1786.
Theſe experiments of Mr. Galton might much aſſiſt the copper-plate printers of callicoes and papers in colours; as three colours or more might be produced by two copper-plates. Thus ſuppoſe ſome yellow figures were put on by the firſt plate, and upon ſome parts of theſe yellow figures and on other parts of the ground blue was laid on by another copper-plate. The three colours of yellow, blue, and green might be produced; as green leaves with yellow and blue flowers.
Eve's ſilken couch with gorgeous tints adorn,Or fire the arrowy throne of riſing morn.CANTO I. l. 119.
THE rays from the riſing and ſetting ſun are refracted by our ſpherical atmoſphere, hence the moſt refrangible rays, as the violet, indigo, and blue are reflected in greater quantities from the morning and evening ſkies; and the leaſt refrangible ones, as red and orange, are laſt ſeen about the ſetting ſun. Hence Mr. Beguelin obſerved that the ſhadow of his finger on his pocket-book was much bluer in the morning and evening, when the ſhadow was about eight times as long as the body from which it was projected. Mr. Melville obſerves, that the blue rays being more refrangible are bent down in the evenings by our atmoſphere, while the red and orange being leſs refrangible continue to paſs on and tinge the morning and evening clouds with their colours. See Prieſtley's Hiſtory of Light and Colours, p. 440. But as the particles of air, like thoſe of water, are themſelves blue, a blue ſhadow may be ſeen at all times of the day, though much more beautifully in the mornings and evenings, or by means of a candle in the middle of the day. For if a ſhadow on a piece of white paper is produced by placing your finger between the paper and a candle in the day light, the ſhadow will appear very blue; the yellow light of the candle upon the other parts of the paper apparently deepens the blue by its contraſt; theſe colours being oppoſite to each other, as explained in note II.
Colours are produced from clouds or miſts by refraction, as well as by reflection. In riding in the night over an unequal country I obſerved a very beautiful coloured halo round the moon, whenever I was covered with a few feet of miſt, as I aſcended from the vallies; which ceaſed to appear when I roſe above the miſt. This I ſuppoſe was owing to the thinneſs of the stratum of miſt, in which I was immerſed; had it been thicker, the colours refracted by the ſmall drops, of which a fog conſiſts, would not have paſſed through it down to my eye.
There is a bright ſpot seen on the cornea of the eye, when we face a window, which is much attended to by portrait painters; this is the light reflected from the ſpherical surface of the poliſhed cornea, and brought to a focus; if the obſerver is placed in this focus, he ſees the image of the window; if he is placed before or behind the focus, he only sees a luminous ſpot, which is more luminous and of leſs extent, the nearer he approaches to the focus. The luminous appearance of the eyes of animals in the duſky corners of a room, or in holes in the earth, may ariſe in ſome inſtances from the same principle; viz. the reflection of the light from the spherical cornea; which will be coloured red or blue in ſome degree by the morning, evening, or meridian light; or by the objects from which that light is previouſly reflected. In the cavern at Colebrook Dale, where the mineral tar exſudes, the eyes of the horſe, which was drawing a cart from within [Page 9] towards the mouth of it, appeared like two balls of phoſphorus, when he was above 100 yards off, and for a long time before any other part of the animal was viſible. In this caſe I suſpect the luminous appearance to have been owing to the light, which had entered the eye, being reflected from the back surface of the vitreous humour, and thence emerging again in parallel rays from the animals eye, as it does from the back surface of the drops of the rainbow, and from the water-drops which lie, perhaps without contact, on cabbage leaves, and have the brilliancy of quickſilver. This accounts for this luminous appearance being beſt seen in thoſe animals which have large apertures in their iris, as in cats and horſes, and is the only part viſible in obſcure places, becauſe this is a better reflecting surface than any other part of the animal. If any of theſe emergent rays from the animals eye can be suppoſed to have been reflected from the choroid coat through the semi-tranſparent retina, this would account for the coloured glare of the eyes of dogs or cats and rabits in dark corners.
Alarm with comet-blaze the ſapphire plain,The wan stars glimmering through its ſilver train.CANTO I. l. 134.
THERE have been many theories invented to account for the tails of comets. Sir Iſaac Newton thinks that they conſiſt of rare vapours raiſed from the nucleus of the comet, and ſo rarefied by the sun's heat as to have their general gravitation diminiſhed, and that they in conſequence aſcend oppoſite to the ſun, and from thence reflect the rays of light. Dr. Halley compares the light of the tails of comets to the ſtreams of the aurora berealis, and other electric effluvia. Philoſ. Tranſ. No. 347.
Dr. Hamilton obſerves that the light of ſmall ſtars are ſeen undiminiſhed through both the light of the tails of comets, and of the aurora borealis, and has further illuſtrated their electric analogy, and adds that the tails of comets conſiſt of a lucid ſelf-ſhining ſubſtance which has not the power of refracting or reflecting the rays of light. Eſſays.
The tail of the comet of 1744 at one time appeared to extend above 16 degrees from its body, and muſt have thence been above twenty three millions of miles long. And the comet of 1680, according to the calculations of Dr. Halley on November the 11th, was not above one ſemi-diameter of the earth, or leſs than 4000 miles to the northward of the way of the earth; at which time had the earth been in that part of its orbit, what might have been the conſequence! no one would probably have ſurvived to have regiſtered the tremendous effects.
[Page 10] The comet of 1531, 1607, and 1682 having returned in the year 1759, according to Dr. Halley's prediction in the Philoſ. Tranſ. for 1705, there ſeems no reaſon to doubt that all the other comets will return after their proper periods. Aſtronomers have in general acquieſced in the conjecture of Dr. Halley, that the comets of 1532, and 1661 are one and the ſame comet, from the ſimilarity of the elements of their orbits, and were therefore induced to expect its return to its perihelium 1789. As this comet is liable to be diſturbed in its aſcent from the ſun by the planets Jupiter and Saturn, Dr. Maſkelyne expected its return to its perihelium in the beginning of the year 1789, or the latter end of the year 1788, and certainly ſometime before the 27th of April, 1789, which prediction has not been fulfilled. Phil. Trans. Vol. LXXVI.
Or give the sun's phlogiſtic orb to roll.CANTO I. l. 136.
THE diſpute among philoſophers about phlogiſton is not concerning the exiſtence of an inflammable principle, but rather whether there be one or more inflammable principles. The diſciples of Stahl, which till lately included the whole chemical world, believed in the identity of phlogiſton in all bodies which would flame or calcine. The diſciples of Lavoiſier pay homage to a plurality of phlogiſtons under the various names of charcoal, sulphur, metals, &c. Whatever will unite with pure air, and thence compoſe an acid, is eſteemed in this ingenious theory to be a different kind of phlogiſtic or inflammable body. At the same time there remains a doubt whether theſe inflammable bodies, as metals, ſulphur, charcoal, &c. may not be compounded of the ſame phlogiſton along with ſome other material yet undiſcovered, and thus an unity of phlogiſton exiſt, as in the theory of Stahl, though very differently applied in the explication of chemical phenomena.
Some modern philoſophers are of opinion that the ſun is the great fountain from which the earth and other planets derive all the phlogiſton which they poſſes; and that this is formed by the combination of the ſolar rays with all opake bodies, but particularly with the leaves of vegetables, which they suppoſe to be organs adapted to abſorb them. And that as animals receive their nouriſhment from vegetables they alſo obtain in a ſecondary manner their phlogiſton from the ſun. And laſtly as great maſſes of the mineral kingdom, which have been found in the thin cruſt of the earth which human labour has penetrated, have evidently been formed from the recrements of animal and vegetable bodies, theſe alſo are suppoſed thus to have derived their phlogiſton from the sun.
Another opinion concerning the ſun's rays is, that they are not luminous till they arrive at our atmoſphere; and that there uniting with ſome part of the air they produce [Page 11] combuſtion, and light is emitted, and that an etherial acid, yet undiſcovered, is formed from this combuſtion.
The more probable opinion is perhaps, that the ſun is a phlogiſtic maſs of matter, whoſe ſurface is in a ſtate of combuſtion, which like other burning bodies emits light with immenſe velocity in all directions; that theſe rays of light act upon all opake bodies, and combining with them either diſplace or produce their elementary heat, and become chemically combined with the phlogiſtic part of them; for light is given out when phlogiſtic bodies unite with the oxygenous principle of the air, as in combuſtion, or in the reduction of metallic calxes; thus in preſenting to the flame of a candle a letterwafer, (if it be coloured with red-lead,) at the time the red-lead becomes a metallic drop, a flaſh of light is perceived. Dr. Alexander Wilſon very ingeniouſly endeavours to prove that the sun is only in a ſtate of combuſtion on its ſurface, and that the dark ſpots ſeen on the diſk are excavations or caverns through the luminous cruſt, some of which are 4000 miles in diameter. Phil. Trans. 1774. Of this I ſhall have occaſion to speak again.
Round her ſtill centre tread the burning ſoil,And watch the billowy Lavas, as they boil.CANTO I. 1. 139.
M. DE MAIRAN in a paper publiſhed in the Hiſtoire de l'Academic de Sciences, 1765, has endeavoured to ſhew that the earth receives but a ſmall part of the heat which it poſſeſſes, from the ſun's rays, but is principally heated by fires within itſelf. He thinks the ſun is the cauſe of the viciſſitudes of our ſeaſons of ſummer and winter by a very ſmall quantity of heat in addition to that already reſiding in the earth, which by emanations from the centre to the circumference renders the ſurface habitable, and without which, though the ſun was conſtantly to illuminate two thirds of the globe at once, with a heat equal to that at the equator, it would ſoon become a maſs of ſolid ice. His reaſonings and calculations on this ſubject are too long and too intricate to be inserted here, but are equally curious and ingenious and carry much conviction along with them.
The opinion that the center of the earth conſiſts of a large maſs of burning lava, has been eſpouſed by Boyle, Boerhave, and many other philoſophers. Some of whom conſidering its ſuppoſed effects on vegetation and the formation of minerals have called it a ſecond ſun. There are many arguments in ſupport of this opinion. 1. Becauſe the power of the ſun does not extend much beyond ten feet deep into the earth, all below being in winter and ſummer always of the ſame degree of heat, viz. 48, which being [Page 12] much warmer than the mildeſt froſt, is ſuppoſed to be ſuſtained by ſome internal diſtant fire. Add to this however that from experiments made ſome years ago by Dr. Franklin the ſpring-water at Philadelphia appeared to be of 52° of heat, which ſeems further to confirm this opinion, ſince the climates in North America are ſuppoſed to be colder than thoſe of Europe under ſimilar degrees of latitude. 2. Mr. De Luc in going 1359 feet perpendicular into the mines of Hartz on July the 5th, 1778, on a very fine day found the air at the bottom a little warmer than at the top of the ſhaft. Phil. Tranſ. Vol. LXIX. p. 488. In the mines in Hungary, which are 500 cubits deep, the heat becomes very troubleſome when the miners get below 480 feet depth. Morinus de Locis ſubter. p. 131. But as ſome other deep mines as mentioned by Mr. Kirwan are ſaid to poſſeſs but the common heat of the earth; and as the cruſt of the globe thus penetrated by human labour is ſo thin compared with the whole, no certain deduction can be made from theſe facts on either ſide of the queſtion. 3. The warm-ſprings in many parts of the earth at great diſtance from any Volcanos ſeem to originate from the condenſation of vapours ariſing from water which is boiled by ſubterraneous fires, and cooled again in their pasſage through a certain length of the colder ſoil; for the theory of chemical ſolution will not explain the equality of their heat at all ſeaſons and through ſo many centuries. See note on Fucus in Vol. II. See a letter on this ſubject in Mr. Pilkinton's View of Derbyſhire from Dr. Darwin. 4. From the ſituations of volcanos which are always found upon the ſummit of the higheſt mountains. For as theſe mountains have been lifted up and loſe ſeveral of their uppermoſt ſtrata as they riſe, the loweſt ſtrata of the earth yet known appear at the tops of the higheſt hills; and the beds of the Volcanos upon theſe hills muſt in conſequence belong to the loweſt ſtrata of the earth, conſiſting perhaps of granite or baſaltes, which were produced before the exiſtance of animal or vegetable bodies, and might conſtitute the original nucleus of the earth, which I have ſuppoſed to have been projected from the ſun, hence the volcanos themſelves appear to be ſpiracula or chimneys belonging to great central fires. It is probably owing to the eſcape of the elaſtic vapours from theſe ſpiracula that the modern earthquakes are of ſuch ſmall extent compared with thoſe of remote antiquity, of which the veſtiges remain all over the globe. 5. The great ſize and height of the continents, and the great ſize and depth of the South-ſea, Atlantic, and other oceans, evince that the firſt earthquakes, which produced theſe immenſe changes in the globe, muſt have been occaſioned by central fires. 6. The very diſtant and expeditious communication of the ſhocks of ſome great earthquakes. The earthquake at Liſbon in 1755 was perceived in Scotland, in the Peak of Derbyſhire, and in many other diſtant parts of Europe. The percuſſions of it travelled with about the velocity of ſound, viz. about thirteen miles in a minute. The earthquake in 1693 extended 2600 leagues. (Goldſmith's Hiſtory.) Theſe phenomena are eaſily explained if the central parts of the earth conſiſt of a fluid lava, as a percuſſion on one part of ſuch a fluid maſs would be felt on other parts of its confining vault, like a ſtroke on a fluid contained in a bladder, which however gentle on one ſide is perceptible to the hand placed on the other; and the velocity with which ſuch a concuſſion would travel would be that of ſound, or thirteen miles in a minute. For further information on this part of the ſubject the reader is referred to Mr. Michell's excellent Treatiſe on Earthquakes in the [Page 13] Philos. Tranſ. Vol. LI. 7. That there is a cavity at the center of the earth is made probable by the late experiments on the attraction of mountains by Mr. Maſkerlyne, who ſuppoſed from other conſiderations that the denſity of the earth near the ſurface ſhould be five times leſs than its mean denſity. Phil. Trans. Vol. LXV. p. 498. But found from the attraction of the mountain Schehallien, that it is probable, the mean denſity of the earth is but double that of the hill. Ibid. p. 532. Hence if the firſt ſuppoſition be well founded there would appear to be a cavity at the centre of conſiderable magnitude, from whence the immenſe beds and mountains of lava, toadſtone, baſaltes, granite, &c. have been protruded. 8. The variation of the compaſs can only be accounted for by ſuppoſing the central parts of the earth to conſiſt of a fluid maſs, and that part of this fluid is iron, which requiring a greater degree of heat to bring it into fuſion than glaſs or other metals, remains a ſolid, and the vis inertiae of this fluid maſs with the iron in it, occaſions it to perform ſewer revolutions than the cruſt of ſolid earth over it, and thus it is gradually left behind, and the place where the floating iron reſides is pointed to by the direct or retrograde motions of the magnetic needle. This ſeems to have been nearly the opinion of Dr. Halley and Mr. Euler.
Or ſphere on ſphere in widening waves expand,And glad with genial warmth the incumbent land.CANTO I. l. 143.
A CERTAIN quantity of heat ſeems to be combined with all bodies beſides the ſenſible quantity which gravitates like the electric fluid amongſt them. This combined heat or latent heat of Dr. Black, when ſet at liberty by fermentation, inflammation, cryſtallization, freezing, or other chemical attractions producing new combinations, paſſes as a fluid element into the ſurrounding bodies. And by thawing, diffuſion of neutral ſalts in water, melting, and other chemical ſolutions, a portion of heat is attracted from the bodies in vicinity and enters into or becomes combined with the new ſolutions.
Hence a combination of metals with acids, of eſſential oils and acids, of alcohol and water, of acids and water, give out heat; whilſt a ſolution of ſnow in water or in acids, and of neutral ſalts in water, attract heat from the ſurrounding bodies. So the acid of nitre mixed with oil of cloves unites with it and produces a moſt violent flame; the ſame acid of nitre poured on ſnow inſtantly diſſolves it and produces the greateſt degree of cold yet known, by which at Peterſburgh quickſilver was firſt frozen in 1760.
Water may be cooled below 32° without being frozen, if it be placed on a ſolid floor and ſecured from agitation, but when thus cooled below the freezing point the leaſt [Page 14] agitation turns part of it ſuddenly into ice, and when this ſudden freezing takes place a thermometer placed in it inſtantly riſes as ſome heat is given out in the act of congelation, and the ice is thus left with the ſame ſenſible degree of cold as the water had poſſeſſed before it was agitated, but is nevertheleſs now combined with leſs latent heat.
A cubic inch of water thus cooled down to 32° mixed with an equal quantity of boiling water at 212° will cool it to the middle number between theſe two, or to 122. But a cubit inch of ice whoſe ſenſible cold alſo is but 32, mixed with an equal quantity of boiling water, will cool it ſix times as much as the cubic inch of cold water abovementioned, as the ice not only gains its ſhare of the ſenſible or gravitating heat of the boiling water but attracts to itſelf alſo and combines with the quantity of latent heat which it had loſt at the time of its congelation.
So boiling water will acquire but 212° of heat under the common preſſure of the atmoſphere, but the ſteam raiſed from it by its expanſion or by its ſolution in the atmoſphere combines with and carries away a prodigious quantity of heat which it again parts with on its condenſation; as is ſeen in common diſtillation where the large quantity of water in the worm-tub is ſo ſoon heated. Hence the evaporation of ether on a thermometer ſoon ſinks the mercury below freezing, and hence a warmth of the air in winter frequently ſucceeds a ſhower.
When the matter of heat or calorique is ſet at liberty from its combinations, as by inflammation, it paſſes into the ſurrounding bodies, which poſſeſs different capacities of acquiring their ſhare of the looſe or ſenſible heat; thus a pint meaſure of cold water at 48° mixed with a pint of boiling water at 212° will cool it to the degree between theſe two numbers, or to 154°, but it requires two pint meaſures of quickſilver at 48° of heat to cool one pint of water as above. Theſe and other curious experiments are adduced by Dr. Black to evince the exiſtance of combined or latent heat in bodies, as has been explained by ſome of his pupils, and well illuſtrated by Dr. Crawford. The world has long been in expectation of an account of his diſcoveries on this ſubject by the celebrated author himſelf.
As this doctrine of elementary heat in its fluid and combined ſtate is not yet univerſally received, I ſhall here add two arguments in ſupport of it drawn from different ſources, viz. from the heat given out or abſorbed by the mechanical condenſation or expanſion of the air, and perhaps of other bodies, and from the analogy of the various phenomena of heat with thoſe of electricity.
I. If a thermometer be placed in the receiver of an air-pump, and the air haſtily exhauſted, the thermometer will ſink ſome degrees, and the glaſs become ſteamy; the ſame occurs in haſtily admitting a part of the air again. This I ſuppoſe to be produced by the expanſion of part of the air, both during the exhauſtion and re-admiſſion of it; and that the air ſo expanded becomes capable of attracting from the bodies in its vicinity a part of their heat, hence the vapours contained in it and the glaſs receiver are for a time colder and the ſteam is precipitated. That the air thus parts with its moiſture from the cold occaſioned by its rarefaction and not ſimply by the rarefaction itſelf is evident, becauſe in a minute or two the ſame rarefied air will again take up the dew depoſited on the receiver; and becauſe water will evaporate ſooner in rare than in denſe air.
[Page 15] There is a curious phenomenon ſimilar to this obſerved in the fountain of Hiero conſtructed on a large ſcale at the Chemnicenſian mines in Hungary. In this machine the air in a large veſſel is compreſſed by a column of water 260 feet high, a ſtop-cock is then opened, and as the air iſſues out with great vehemence, and thus becomes immediately greatly expanded, ſo much cold is produced that the moiſture from this ſtream of air is precipitated in the form of ſnow, and ice is formed adhering to the noſel of the cock. This remarkable circumſtance is deſcribed at large with a plate of the machine in Philos. Trans. Vol. LII. for 1761.
The following experiment is related by Dr. Darwin in the Philos. Trans. Vol. LXXVIII. Having charged an air-gun as forcibly as he well could the air-cell and ſyringe became exceedingly hot, much more ſo than could be aſcribed to the friction in working it; it was then left about half an hour to cool down to the temperature of the air, and a thermometer having been previouſly fixed againſt a wall, the air was diſcharged in a continual ſtream on its bulb, and it ſunk many degrees. From theſe three experiments of the ſteam in the exhauſtéd receiver being depoſited and re-abſorbed, when a part of the air is exhauſted or re-admitted, and the ſnow produced by the fountain of Hiero, and the extraordinary heat given out in charging, and the cold produced in diſcharging an air-gun, there is reaſon to conclude that when air is mechanically compreſſed the elementary fluid heat is preſſed out of it, and that when it is mechanically expanded the ſame fluid heat is re-abſorbed from the common maſs.
It is probable all other bodies as well as air attract heat from their neighbours when they are mechanically expanded, and give it out when they are mechanically condenſed. Thus when a vibration of the particles of hard bodies is excited by friction or by percuſſion, theſe particles mutually recede from and approach each other reciprocally; at the times of their receſſion from each other, the body becomes enlarged in bulk, and is then in a condition to attract heat from thoſe in its vicinity with great and ſudden power; at the times of their approach to each other this heat is again given out, but the bodies in contact having in the mean while received the heat they had thus loſt, from other bodies behind them, do not ſo ſuddenly or ſo forcibly re-abſorb the heat again from the body in vibration; hence it remains on its ſurface like the electric fluid on a rubbed glaſs globe, and for the ſame reaſon, becauſe there is no good conductor to take it up again. Hence at every vibration more and more heat is acquired and ſtands looſe upon the ſurface; as in filing metals or rubbing glaſs tubes; and thus a ſmith with a few ſtrokes on a nail on his anvil can make it hot enough to light a brimſtone-match; and hence in ſtriking flint and ſteel together heat enough is produced to vitrify the parts thus ſtrucken off, the quantity of which heat is again probably increaſed by the new chemical combination.
II. The analogy between the phenomena of the electric fluid and of heat furniſhes another argument in ſupport of the exiſtence of heat as a gravitating fluid. 1. They are both accumulated by friction on the excited body. 2. They are propagated eaſily or with difficalty along the ſame claſſes of bodies; with eaſe by metals, with leſs eaſe by water; and with difficulty by reſins, bees-wax, ſilk, air, and glaſs. Thus glaſs canes or canes of ſealing-wax may be melted by a blow-pipe or a candle within a quarter of an [Page 16] inch of the fingers which hold them, without any inconvenient heat, while a pin or other metallic ſubſtance applyed to the flame of a candle ſo readily conducts the heat as immediately to burn the fingers. Hence clothes of ſilk keep the body warmer than clothes of linen of equal thickneſs, by confining the heat upon the body. And hence plains are ſo much warmer than the ſummits of mountains by the greater denſity of the air confining the acquired heat upon them. 3. They both give out light in their paſſage through air, perhaps not in their paſſage through a vacuum. 4. They both of them fuſe or vitrify metals. 5. Bodies after being electrized if they are mechanically extended will receive a greater quantity of electricity, as in Dr. Franklin's experiment of the chain in the tankard; the ſame ſeems true in reſpect to heat as explained above. 6. Both heat and electricity contribute to ſuſpend ſteam in the atmoſphere by producing or increaſing the repulſion of its particles. 7. They both gravitate, when they have been accumulated, till they find their equilibrium.
If we add to the above the many chemical experiments which receive an eaſy and elegant explanation from the ſuppoſed matter of heat, as employed in the works of Bergman and Lavoiſier, I think we may reaſonably allow of its exiſtence as an element, occaſionally combined with other bodies, and occaſionally exiſting as a fluid, like the electric fluid gravitating amongſt them, and that hence it may be propagated from the central fires of the earth to the whole maſs, and contribute to preſerve the mean heat of the earth, which in this country is about 48 degrees but variable from the greater or leſs effect of the ſun's heat in different climates, ſo well explained in Mr. Kirwan's Treatiſe on the Temperature of different Latitudes. 1787, Elmſly. London.
So to the ſacred Sun in Memnon's faneSpontaneous concords quired the matin ſtrain.CANTO I. l. 181.
THE gigantic ſtatue of Memnon in his temple at Thebes had a lyre in his hands, which many credible writers aſſure us, ſounded when the riſing ſun ſhone upon it. Some philoſophers have ſuppoſed that the ſun's light poſſeſſes a mechanical impulſe, and that the ſounds abovementioned might be thence produced. Mr. Michell conſtructed a very tender horizontal balance, as related by Dr. Prieſtley in his hiſtory of light and colours, for this purpoſe, but ſome experiments with this balance which I ſaw made by the late Dr. Powel, who threw the focus of a large reflector on one extremity of it, were not concluſive eitherway, as the copper leaf of the balance approached in one experiment and receded in another.
There are however methods by which either a rotative or alternating motion may be produced by very moderate degrees of heat. If a ſtraight glaſs tube, ſuch as are uſed for barometers, be ſuſpended horizontally before a fire, like a roaſting ſpit, it will revolve by intervals; for as glaſs is a bad conductor of heat the ſide next the fire becomes heated ſooner than the oppoſite ſide, and the tube becomes bent into a bow with the external part of the curve towards the fire, this curve then falls down and produces a fourth part of a revolution of the glaſs tube, which thus revolves with intermediate pauſes.
Another alternating motion I have ſeen produced by ſuſpending a glaſs tube about eight inches long with bulbs at each end on a centre like a ſcale beam. This curious machine is filled about one third part with pureſt ſpirit of wine, the other two thirds being a vacuum, and is called a pulſe-glaſs, if it be placed in a box before the fire, ſo that either bulb, as it riſes, may become ſhaded from the fire, and expoſed to it when it deſcends, an alternate libration of it is produced. For ſpirit of wine in vacuo emits ſteam by a very ſmall degree of heat, and this ſteam forces the ſpirit beneath it up into the upper bulb, which therefore deſcends. It is probable ſuch a machine on a larger ſcale might be of uſe to open the doors or windows of hot-houſes or mellon-frames, when the air within them ſhould become too much heated, or might be employed in more important mechanical purpoſes.
On travelling through a hot ſummer's day in a chaiſe with a box covered with leather on the fore-axle-tree, I obſerved, as the ſun ſhone upon the black leather, the box began to open its lid, which at noon roſe above a foot, and could not without great force be preſſed down; and which gradually cloſed again as the ſun declined in the evening. This I ſuppoſe might with ſtill greater facility be applied to the purpoſe of opening melonframes or the ſaſhes of hot-houſes.
The ſtatue of Memnon was overthrown and ſawed in two by Cambyſes to diſcover its internal ſtructure, and is ſaid ſtill to exiſt. See Savary's Letters on Egypt. The truncated ſtatue is ſaid for many centuries to have ſaluted the riſing ſun with chearful tones, and the ſetting ſun with melancholy ones.
Star of the earth, and diamond of the night.CANTO I. l. 192.
THERE are eighteen ſpecies of Lampyris or glow-worm, according to Linneus, ſome of which are found in almoſt every part of the world. In many of the ſpecies the females have no wings, and are ſuppoſed to be diſcovered by the winged males by their ſhining in the night. They become much more lucid when they put themſelves in motion, which would ſeem to indicate that their light is owing to their reſpiration; in which proceſs it is probable phoſphoric acid is produced by the combination of vital air with ſome part of the blood, and that light is given out through their tranſparent bodies by this ſlow internal combuſtion.
There is a fire-fly of the beetle-kind deſcribed in the Dict. Raiſonné under the name of Acudia, which is ſaid to be two inches long, and inhabits the Weſt-Indies and South America; the natives uſe them inſtead of candles, putting from one to three of them under a glaſs. Madam Merian ſays, that at Surinam the light of this fly is ſo great, that ſhe ſaw ſufficiently well by one of them to paint and finiſh one of the figures of them in her work on inſects. The largeſt and oldeſt of them are ſaid to become four inches long, and to ſhine like a ſhooting ſtar as they fly, and are thence called Lanternbearers. The uſe of this light to the inſect itſelf ſeems to be that it may not fly againſt objects in the night; by which contrivance theſe inſects are enabled to procure their ſuſtenance either by night or day, as their wants may require, or their numerous enemies permit them; whereas ſome of our beetles have eyes adapted only to the night, and if they happen to come abroad too ſoon in the evening are ſo dazzled that they fly againſt every thing in their way. See note on Phoſphorus, No. X.
In ſome ſeas, as particularly about the coaſt of Malabar, as a ſhip floats along, it ſeems during the night to be ſurrounded with fire, and to leave a long tract of light behind it. Whenever the ſea is gently agitated it ſeems converted into little ſtars, every drop as it breaks emits light, like bodies electrified in the dark. Mr. Bomare ſays, that when he was at the port of Cettes in Languedoc, and bathing with a companion in the ſea after a very hot day, they both appeared covered with fire after every immerſion, and that laying his wet hand on the arm of his companion, who had not then dipped himſelf, the exact mark of his hand and fingers was ſeen in characters of fire. As numerous microſcopic inſects are found in this ſhining water, its light has been generally aſcribed to them, though it ſeems probable that fiſh-ſlime in hot countries may become in ſuch a ſtate of incipient putrefaction as to give light, eſpecially when by agitation it is more expoſed to the air; otherwiſe it is not eaſy to explain why agitation ſhould be neceſſary to produce this marine light. See note on Phoſphorus No. X.
Or mark in ſhining letters Kunckel's nameIn the pale phoſphor's ſelf-conſuming flame.CANTO I. l. 237.
KUNCKEL, a native of Hamburgh, was the firſt who diſcovered to the world the proceſs for producing phoſphorus; though Brandt and Boyle were likewiſe ſaid to have previouſly had the art of making it. It was obtained from ſal microcoſmicum by evaporation in the form of an acid, but has ſince been found in other animal ſubſtances, as in the aſhes of bones, and even in ſome vegetables, as in wheat flour. Keir's chemical Dict. This phoſphoric acid is like all other acids united with vital air, and requires to be treated with charcoal or phlogiſton to deprive it of this air, it then becomes a kind of animal ſulphur, but of ſo inflammable a nature, that on the acceſs of air it takes fire ſpontaneouſly, and as it burns becomes again united with vital air, and re-aſſumes its form of phoſphoric acid.
As animal reſpiration ſeems to be a kind of ſlow combuſtion, in which it is probable that pboſphoric acid is produced by the union of phoſphorus with the vital air, ſo it is alſo probable that phoſphoric acid is produced in the excretory or reſpiratory veſſels of luminous inſects, as the glow-worm and fire-fly, and ſome marine inſects. From the ſame principle I ſuppoſe the light from putrid fiſh, as from the heads of hadocks, and from putrid veal, and from rotten wood in a certain ſtate of their putrefaction, is produced, and phoſphorus thus ſlowly combined with air is changed into phoſphoric acid. The light from the Bolognian ſtone, and from calcined ſhells, and from white paper, and linen after having been expoſed for a time to the ſun's light, ſeem to produce either the phoſphoric or ſome other kind of acid from the ſulphurous or phlogiſtic matter which they contain. See note on Beccari's ſhells. l. 180.
There is another proceſs ſeems ſimilar to this ſlow combuſtion, and that is bleaching. By the warmth and light of the ſun the water ſprinkled upon linen or cotton cloth ſeems to be decompoſed, (if we credit the theory of M. Lavoiſier,) and a part of the vital air thus ſet at liberty and uncombined and not being in its elaſtic form, more eaſily diſſolves the colouring or phlogiſtic matter of the cloth, and produces a new acid, which is itſelf colourleſs, or is waſhed out of the cloth by water. The new proceſs of bleaching confirms a part of this theory, for by uniting much vital air to marine acid by diſtilling it from manganeſe, on dipping the cloth to be bleached in water repleat with this ſuperaerated marine acid, the colouring matter diſappears immediately, ſooner indeed in cotton than in linen. See note XXXIV.
There is another proceſs which I ſuſpect bears analogy to theſe above-mentioned, and that is the rancidity of animal fat, as of bacon; if bacon be hung up in a warm kitchen, with much ſalt adhering on the outſide of it, the fat part of it ſoon becomes [Page 20] yellow and rancid; if it be waſhed with much cold water after it has imbibed the ſalt, and juſt before it is hung up, I am well informed, that it will not become rancid, or in very ſlight degrees. In the former caſe I imagine the ſalt on the ſurface of the bacon attracts water during the cold of the night, which is evaporated during the day, and that in this evaporation a part of the water becomes decompoſed, as in bleaching, and its vital air uniting with greater facility in its unelaſtic ſtate with the animal fat, produces an acid, perhaps of the phoſphoric kind, which being of a fixed nature lies upon the bacon, giving it the yellow colour and rancid taſte. It is remarkable that the ſuperaerated marine acid does not bleach living animal ſubſtances, at leaſt it did not whiten a part of my hand which I for ſome minutes expoſed to it.
Quick moves the balanced beam, of giant-birth,Wields his large limbs, and nodding ſhakes the earth.CANTO I. l. 267.
THE expanſive force of ſteam was known in ſome degree to the antients, Hero of Alexandria deſcribes an application of it to produce a rotative motion by the re-action of ſteam iſſuing from a ſphere mounted upon an axis, through two ſmall tubes bent into tangents, and iſſuing from the oppoſite ſides of the equatorial diameter of the ſphere, the ſphere was ſupplied with ſteam by a pipe communicating with a pan of boiling water, and entering the ſphere at one of its poles.
A french writer about the year 1630 deſcribes a method of raiſing water to the upper part of a houſe by filling a chamber with ſteam, and ſuffering it to condenſe of itſelf, but it ſeems to have been mere theory, as his method was ſcarcely practicable as he deſcribes it. In 1655 the Marquis of Worceſter mentions a method of raiſing water by fire in his Century of Inventions, but he ſeems only to have availed himſelf of the expanſive force and not to have known the advantages ariſing from condenſing the ſteam by an injection of cold water. This latter and moſt important improvement ſeems to have been made by Capt. Savery ſometime prior to 1698, for in that year his patent for the uſe of that invention was confirmed by act of parliament. This gentleman appears to have been the firſt who reduced the machine to practice and exhibited it in an uſeful form. This method conſiſted only in expelling the air from a veſſel by ſteam and condenſing the ſteam by an injection of cold water, which making a vacuum, the preſſure of the atmoſphere forced the water to aſcend into the ſteam-veſſel through a pipe of 24 to 26 feet [Page 21] high, and by the admiſſion of denſe ſteam from the boiler, forcing the water in the ſteamveſſel to aſcend to the height deſired. This conſtruction was defective becauſe it required very ſtrong veſſels to reſiſt the force of the ſteam, and becauſe an enormous quantity of ſteam was condenſed by coming in contact with the cold water in the ſteam-veſſel.
The next improvement was made very ſoon afterwards by Meſſrs. Newcomen and Cawley of Dartmouth, it conſiſted in employing for the ſteam-veſſel a hollow cylinder, ſhut at bottom and open at top, furniſhed with a piſton ſliding eaſily up and down in it, and made tight by oakum or hemp, and covered with water. This piſton is ſuſpended by chains from one end of a beam, moveable upon an axis in the middle of its length, to the other end of this beam are ſuſpended the pump-rods.
The danger of burſting the veſſels was avoided in this machine, as however high the water was to be raiſed it was not neceſſary to increaſe the denſity of the ſteam but only to enlarge the diameter of the cylinder.
The machine however ſtill remained imperfect, for the cold water thrown into the cylinder acquired heat from the ſteam it condenſed, and being in a veſſel exhauſted of air it produced ſteam itſelf, which in part reſiſted the action of the atmoſphere on the piſton; were this remedied by throwing in more cold water the deſtruction of ſteam in the next filling of the cylinder would be proportionally increaſed. It has therefore in practice been found adviſeable not to load theſe engines with columns of water weighing more than ſeven pounds for each ſquare inch of the area of the piſton. The bulk of water when converted into ſteam remained unknown until Mr. J. Watt, then of Glaſgow, in 1764, determined it to be about 1800 times more rare than water. It ſoon occurred to Mr. Watt that a perfect engine would be that in which no ſteam ſhould be condenſed in filling the cylinder, and in which the ſteam ſhould be ſo perfectly cooled as to produce nearly a perfect vacuum.
Mr. Watt having aſcertained the degree of heat in which water boiled in vacuo, and under progreſſive degrees of preſſure, and inſtructed by Dr. Black's diſcovery of latent heat, having calculated the quantity of cold water neceſſary to condenſe certain quantities of ſteam ſo far as to produce the exhauſtion required, he made a communication from the cylinder to a cold veſſel previouſly exhauſted of air and water, into which the ſteam ruſhed by its elaſticity, and became immediately condenſed. He then adapted a cover to the cylinder and admitted ſteam above the piſton to preſs it down inſtead of air, and inſtead of applying water he uſed oil or greaſe to fill the pores of the oakum and to lubricate the cylinder.
[Page 22] To prevent the cooling of the cylinder by the contact of the external air, he ſurrounded it with a caſe containing ſteam, which he again protected by a covering of matters which conduct heat ſlowly.
This conſtruction preſented an eaſy means of regulating the power of the engine, for the ſteam being the acting power, as the pipe which admits it from the boiler is more or leſs opened, a greater or ſmaller quantity can enter during the time of a ſtroke, and conſequently the engine can act with exactly the neceſſary degree of energy.
Mr. Watt gained a patent for his engine in 1768, but the further perſecution of his deſigns were delayed by other avocations till 1775, when in conjunction with Mr. Boulton of Soho near Birmingham, numerous experiments were made on a large ſcale by their united ingenuity, and great improvements added to the machinery, and an act of parliament obtained for the prolongation of their patent for twenty-five years, they have ſince that time drained many of the deep mines in Cornwall, which but for the happy union of ſuch genius muſt immediately have ceaſed to work. One of theſe engines works a pump of eighteen inches diameter, and upwards of 100 fathom or 600 feet high, at the rate of ten to twelve ſtrokes of ſeven feet long each, in a minute, and that with one fifth part of the coals which a common engine would have taken to do the ſame work. The power of this engine may be eaſier comprehended by ſaying that it raiſed a weight equal to 81000 pounds 80 feet high in a minute, which is equal to the combined action of 200 good horſes. In Newcomen's engine this would have required a cylinder of the enormous diameter of 120 inches or ten feet, but as in this engine of Mr. Watt and Mr. Boulton the ſteam acts, and a vacuum is made, alternately above and below the piſton, the power exerted is double to what the ſame cylinder would otherways produce, and is further augmented by an inequality in the length of the two ends of the lever.
Theſe gentlemen have alſo by other contrivances applied their engines to the turning of mills for almoſt every purpoſe, of which that great pile of machinery the Albion Mill is a well known inſtance. Forges, ſlitting mills, and other great works are erected where nature has furniſhed no running water, and future times may boaſt that this grand and uſeful engine was invented and perfected in our own country.
Since the above article went to the preſs the Albion Mill is no more; it is ſuppoſed to have been ſet on fire by intereſted or malicious incendaries, and is burnt to the ground. Whence London has loſt the credit and the advantage of poſſeſſing the moſt powerful machine in the world!
In phalanx firm the fiend of Froſt aſſail.CANTO I. l. 446.
THE cauſe of the expanſion of water during its converſion into ice is not yet well aſcertained, it was ſuppoſed to have been owing to the air being ſet at liberty in the act of congelation which was before diſſolved in the water, and the many air bubbles in ice were thought to countenance this opinion. But the great force with which ice expands during its congelation, ſo as to burſt iron bombs and coehorns, according to the experiments of Major Williams at Quebec, invalidates this idea of the cauſe of it, and may ſometime be brought into uſe as a means of breaking rocks in mining, or projecting cannon-balls, or for other mechanical purpoſes, if the means of producing congelation ſhould ever be diſcovered to be as eaſy as the means of producing combuſtion.
Mr. de Mairan attributes the increaſe of bulk of frozen water to the different arrangement of the particles of it in cryſtallization, as they are conſtantly joined at an angle of 60 degrees; and muſt by this diſpoſition he thinks occupy a greater volume than if they were parallel. He found the augmentation of the water during freezing to amount to one-fourteenth, one-eighteenth, one-nineteenth, and when the water was previouſly purged of air to only one-twenty-ſecond part. He adds that a piece of ice, which was at firſt only one-fourteenth part ſpecifically lighter than water, on being expoſed ſome days to the froſt became one-twelfth lighter than water. Hence he thinks ice by being expoſed to greater cold ſtill increaſes in volume, and to this attributes the burſting of ice in ponds and on the glaciers. See Lewis's Commerce of Arts, p. 257. and the note on Muſchus in the other volume of this work.
This expanſion of ice well accounts for the greater miſchief done by vernal froſts attended with moiſture, (as by hoar-froſts,) than by the dry froſts called black froſts. Mr. Lawrence in a letter to Mr. Bradley complains that the dale-miſt attended with a froſt on may-day had deſtroyed all his tender fruits; though there was a ſharper froſt the night before without a miſt, that did him no injury; and adds, that a garden not a ſtone's throw from his own on a higher ſituation, being above the dale-miſt, had received no damage. Bradley, Vol. II. p. 232.
Mr. Hunter by very curious experiments diſcovered that the living principle in fiſh, in vegetables, and even in eggs and ſeeds, poſſeſſes a power of reſiſting congelation. Phil. Tranſ. There can be no doubt but that the exertions of animals to avoid the pain of cold may produce in them a greater quantity of heat, at leaſt for a time, but that vegetables, eggs, or ſeeds, ſhould poſſeſs ſuch a quality is truly wonderful. Others have imagined that animals poſſeſs a power of preventing themſelves from becoming much warmer than 98 degrees of heat, when immerſed in an atmoſphere above that degree of heat. It is true that the increaſed exhalation from their bodies will in ſome meaſure cool them, as much heat is carried off by the evaporation of fluids, but this is a chemical not an animal proceſs. The experiments made by thoſe who continued [Page 24] many minutes in the air of a room heated ſo much above any natural atmoſpheric heat, do not ſeem concluſive, as they remained in it a leſs time than would have been necesſary to have heated a maſs of beef of the ſame magnitude, and the circulation of the blood in living animals, by perpetually bringing new ſupplies of fluid to the ſkin, would prevent the external ſurface from becoming hot much ſooner than the whole maſs. And thirdly, there appears no power of animal bodies to produce cold in diſeaſes, as in ſcarlet fever, in which the increaſed action of the veſſels of the ſkin produces heat and contributes to exhauſt the animal power already too much weakened.
It has been thought by many that froſts meliorate the ground, and that they are in general ſalubrious to mankind. In reſpect to the former it is now well known that ice or ſnow contain no nitrous particles, and though froſt by enlarging the bulk of moiſt clay leaves it ſofter for a time after the thaw, yet as ſoon as the water exhales, the clay becomes as hard as before, being preſſed together by the incumbent atmoſphere, and by its ſelfattraction, called ſetting by the potters. Add to this that on the coaſts of Africa, where froſt is unknown, the fertility of the ſoil is almoſt beyond our conceptions of it. In reſpect to the general ſalubrity of froſty ſeaſons the bills of mortality are an evidence in the negative, as in long froſts many weakly and old people periſh from debility occaſioned by the cold, and many claſſes of birds and other wild animals are benumbed by the cold or deſtroyed by the conſequent ſcarcity of food, and many tender vegetables periſh from the degree of cold.
I do not think it ſhould be objected to this doctrine that there are moiſt days attended with a briſk cold wind when no viſible ice appears, and which are yet more diſagreeable and deſtructive than froſty weather. For on theſe days the cold moiſture, which is depoſited on the ſkin is there evaporated and thus produces a degree of cold perhaps greater than the milder froſts. Whence even in ſuch days both the diſagreeable ſenſations and inſalubrious effects belong to the cauſe abovementioned, viz. the intenſity of the cold. Add to this that in theſe cold moiſt days as we paſs along or as the wind blows upon us, a new ſheet of cold water is as it were perpetually applied to us and hangs upon our bodies, now as water is 800 times denſer than air and is a much better conductor of heat, we are ſtarved with cold like thoſe who go into a cold bath, both by the great number of particles in contact with the ſkin and their greater facility of receiving our heat.
It may nevertheleſs be true that ſnows of long duration in our winters may be leſs injurious to vegetation than great rains and ſhorter froſts, for two reaſons. 1. Becauſe great rains carry down many thouſand pounds worth of the beſt part of the manure off the lands into the ſea, whereas ſnow diſſolves more gradually and thence carries away leſs from the land; any one may diſtinguiſh a ſnow-flood from a rain-flood by the tranſparency of the water. Hence hills or fields with conſiderable inclination of ſurface ſhould be ploughed horizontally that the furrows may ſtay the water from ſhowers till it depoſits its mud. 2. Snow protects vegetables from the ſeverity of the froſt, ſince it is always in a ſtate of thaw where it is in contact with the earth; as the earth's heat is about 48° and the heat of thawing ſnow is 32° the vegetables between them are kept in a degree of heat about 40, by which many of them are preſerved. See note on Muſchus, Vol. II. of this work.
Cold from each point cerulean luſtres gleam.CANTO I. l. 345.
THERE was an idle diſpute whether knobs or points were preferable on the top of conductors for the defence of houſes. The deſign of theſe conductors is to permit the electric matter accumulated in the clouds to paſs through them into the earth in a ſmaller continued ſtream as the cloud approaches, before it comes to what is termed ſtriking diſtance; now as it is well known that accumulated electricity will paſs to points at a much greater diſtance than it will to knobs there can be no doubt of their preference; and it would ſeem that the finer the point and the leſs liable to become ruſty the better, as it would take off the lightening while it was ſtill at a greater diſtance, and by that means preſerve a greater extent of building; the very extremity of the point ſhould be of pure ſilver or gold, and might be branched into a kind of bruſh, ſince one ſmall point can not be ſuppoſed to receive ſo great a quantity as a thicker bar might conduct into the earth.
If an inſulated metallic ball is armed with a point, like a needle, projecting from one part of it, the electric fluid will be ſeen in the dark to paſs off from this point, ſo long as the ball is kept ſupplied with electricity. The reaſon of this is not difficult to comprehend, every part of the electric atmoſphere which ſurrounds the inſulated ball is attracted to that ball by a large ſurface of it, whereas the electric atmoſphere which is near the extremity of the needle is attracted to it by only a ſingle point, in conſequence the particles of electric matter near the ſurface of the ball approach towards it and puſh off by their greater gravitation the particles of electric matter over the point of the needle in a continued ſtream.
Something like this happens in reſpect to the diffuſion of oil on water from a pointed cork, an experiment which was many years ago ſhewn me by Dr. Franklin; he cut a piece of cork about the ſize of a letter-wafer and left on one edge of it a point about a ſixth of an inch in length projecting as a tangent to the circumference. This was dipped in oil and thrown on a pond of water and continued to revolve as the oil left the point for a great many minutes. The oil deſcends from the floating cork upon the water being diffuſed upon it without friction and perhaps without contact; but its going off at the point ſo forcibly as to make the cork revolve in a contrary direction ſeems analogous to the departure of the electric fluid from points.
Can any thing ſimilar to either of theſe happen in reſpect to the earth's atmoſphere and give occaſion to the breezes on the tops of mountains, which may be conſidered as points on the earths circumference?
There is a phenomenon ſuppoſed to be electric which is yet unaccounted for, I mean the Fairy-rings, as they are called, ſo often ſeen on the graſs. The numerous flaſhes of lightning which occur every ſummer are, I believe, generally diſcharged on the earth, and but ſeldom (if ever) from one cloud to another. Moiſt trees are the moſt frequent conductors of theſe flaſhes of lightning, and I am informed by purchaſers of wood that innumerable trees are thus cracked and injured. At other times larger parts or prominences of clouds gradually ſinking as they move along, are diſcharged on the moiſture parts of graſſy plains. Now this knob or corner of a cloud in being attracted by the earth will become nearly cylindrical, as looſe wool would do when drawn out into a thread, and will ſtrike the earth with a ſtream of electricity perhaps two or ten yards in diameter. Now as a ſtream of electricity diſplaces the air it paſſes through, it is plain no part of the graſs can be burnt by it, but juſt the external ring of this cylinder where the graſs can have acceſs to the air, ſince without air nothing can be calcined. This earth after having been ſo calcined becomes a richer ſoil, and either funguſes or a bluer graſs for many years mark the place. That lightning diſplaces the air in its paſſage is evinced by the loud crack that ſucceeds it, which is owing to the ſides of the aerial vacuum clapping together when the lightning is withdrawn. That nothing will calcine without air is now well underſtood from the acids produced in the burning of phlogiſtic ſubſtances, and may be agreeably ſeen by ſuſpending a paper on an iron prong and putting it into the centre of the blaze of an iron-furnace; it may be held there ſome ſeconds and may be again withdrawn without its being burnt, if it be paſſed quickly into the flame and out again through the external part of it which is in contact with the air. I know ſome circles of many yards diameter of this kind near Foremark in Derbyſhire which annually produce large white funguſes and ſtronger graſs, and have done ſo, I am informed, above thirty years. This increaſed fertility of the ground by calcination or charring, and its continuing to operate ſo many years is well worth the attention of the farmer, and ſhews the uſe of paring and burning new turf in agriculture, which produces its effect not ſo much by the aſhes of the vegetable fibres as by charring the ſoil which adheres to them.
Theſe ſituations, whether from eminence or from moiſture, which were proper once to attract and diſcharge a thunder-cloud, are more liable again to experience the ſame. Hence many fairy-rings are often ſeen near each other either without interſecting each other, as I ſaw this ſummer in a garden in Nottinghamſhire, or interſecting each other as deſcribed on Arthur's ſeat near Edinburgh in the Edinb. Tranſ. Vol. II. p. 3.
Where dwell my vegetative realms benumb'dIn buds impriſon'd, or in bulbs intomb'd.CANTO I. l. 465.
A TREE is properly ſpeaking a family or ſwarm of buds, each bud being an individual plant, for if one of theſe buds be torn or cut out and planted in the earth with a glaſs cup inverted over it to prevent its exhalation from being at firſt greater than its power of abſorption, it will produce a tree ſimilar to its parent; each bud has a leaf, which is its lungs, appropriated to it, and the bark of the tree is a congeries of the roots of theſe individual buds, whence old hollow trees are often ſeen to have ſome branches flouriſh with vigour after the internal wood is almoſt intirely decayed and vaniſhed. According to this idea Linneus has obſerved that trees and ſhrubs are roots above ground, for if a tree be inverted leaves will grow from the root-part and roots from the trunk-part. Phil. Bot. p. 39. Hence it appears that vegetables have two methods of propagating themſelves, the oviparous as by ſeeds, and the viviparous as by their buds and bulbs, and that the individual plants, whether from ſeeds or buds or bulbs, are all annual productions like many kinds of inſects as the ſilk-worm, the parent periſhing in the autumn after having produced an embryon, which lies in a torpid ſtate during the winter, and is matured in the ſucceeding ſummer. Hence Linneus names buds and bulbs the winter-cradles of the plant or hybernacula, and might have given the ſame term to ſeeds. In warm climates few plants produce buds, as the vegetable life can be compleated in one ſummer, and hence the hybernacle is not wanted; in cold climates alſo ſome plants do not produce buds, as philadelphus, ſrangula, viburnum, ivy, heath, wood-nightſhade, rue, geranium.
The bulbs of plants are another kind of winter-cradle, or hybernacle, adhering to the deſcending trunk, and are found in the perennial herbaceous plants which are too tender to bear the cold of the winter. The production of theſe ſubterraneous winter lodges, is not yet perhaps clearly underſtood, they have been diſtributed by Linneus according to their forms into ſcaly, ſolid, coated, and jointed bulbs, which however does not elucidate their manner of production. As the buds of trees may be truly eſteemed individual annual plants, their roots conſtituting the bark of the tree, it follows that theſe roots (viz. of each individual bud) ſpread themſelves over the laſt years bark, making a new bark over the old one, and thence deſcending cover with a new bark the old roots alſo in the ſame manner. A ſimilar circumſtance I ſuppoſe to happen in ſome herbaceous plants, that is, a new bark is annually produced over the old root, and thus for ſome years at leaſt the old root or caudex increaſes in ſize and puts up new ſtems. As theſe roots increaſe in ſize the central part I ſuppoſe changes like the internal wood of a tree and does not poſſeſs any vegetable life, and therefore gives out no fibres or rootlets, and hence appears bitten off, as in valerian, plantain, and devil's-bit. And this decay of the central part of the root I ſuppoſe has given occaſion to the belief of the root-fibres drawing down the bulb ſo much inſiſted on by Mr. Milne in his Botanical Dictionary, Art. Bulb.
[Page 28] From the obſervations and drawings of various kinds of bulbous roots at different times of their growth, ſent me by a young lady of nice obſervation, it appears probable that all bulbous roots properly ſo called periſh annually in this climate: Bradley, Miller, and the Author of Spectacle de la Nature, obſerve that the tulip annually renews its bulb, for the ſtalk of the old flower is found under the old dry coat but on the outſide of the new bulb. This large new bulb is the flowering bulb, but beſides this there are other ſmall new bulbs produced between the coats of this large one but from the ſame caudex, (or circle from which the root-fibres ſpring;) theſe ſmall bulbs are leaf-bearing bulbs, and renew themſelves annually with increaſing ſize till they bear flowers.
Miſs—favoured me with the following curious experiment: She took a ſmall tulip-root out of the earth when the green leaves were ſufficiently high to ſhow the flower, and placed it in a glaſs of water; the leaves and flower ſoon withered and the bulb became wrinkled and ſoft, but put out one ſmall ſide bulb and three bulbs beneath deſcending an inch into the water by long proceſſes from the caudex, the old bulb in ſome weeks intirely decayed; on diſſecting this monſter, the middle deſcending bulb was found by its proceſs to adhere to the caudex and to the old flower-ſtem, and the ſide ones were ſeparated from the flower-ſtem by a few ſhrivelled coats but adhered to the caudex. Whence ſhe concludes that theſe laſt were off-ſets or leaf-bulbs which ſhould have been ſeen between the coats of the new flower-bulb if it had been left to grow in the earth, and that the middle one would have been the new flower-bulb. In ſome years (perhaps in wet ſeaſons) the floriſts are ſaid to loſe many of their tulip-roots by a ſimilar proceſs, the new leaf-bulbs being produced beneath the old ones by an elongation of the caudex without any new flower-bulbs.
By repeated diſſections ſhe obſerves that the leaf-bulbs or off-ſets of tulip, crocus, gladiolus, fritillary, are renewed in the ſame manner as the flowering-bulbs, contrary to the opinion of many writers; this new leaf-bulb is formed on the inſide of the coats from whence the leaves grow, and is more or leſs advanced in ſize as the outer coats and leaves are more or leſs ſhrivelled. In examining tulip, iris, hyacinth, hare-bell, the new bulb was invariably found between the flower-ſtem and the baſe of the innermoſt leaf of thoſe roots which had flowered, and incloſed by the baſe of the innermoſt leaf in thoſe roots which had not flowered, in both caſes adhering to the caudex or fleſhy circle from which the root-fibres ſpring.
Hence it is probable that the bulbs of hyacinths are renewed annually, but that this is performed from the caudex within the old bulb, the outer coat of which does not ſo ſhrivel as in crocus and fritillary and hence this change is not ſo apparent. But I believe as ſoon as the flower is advanced the new bulbs may be ſeen on diſſection, nor does the annual increaſe of the ſize of the root of cyclamen and of aletris capenſis militate againſt this annual renewal of them, ſince the leaf-bulbs or off-ſets, as deſcribed above, are increaſed in ſize as they are annually renewed. See note on orchis, and on anthoxanthum, in Vol. II. of this work.
From the deep craters of his realms of fireThe whirling ſun this ponderous planet hurld.CANTO II. l. 14.
DR. ALEXANDER WILSON, Profeſſor of Aſtronomy at Glaſgow, publiſhed a paper in the Philoſophical Tranſactions for 1774, demonſtrating that the ſpots in the ſun's diſk are real cavities, excavations through the luminous material, which covers the other parts of the ſun's ſurface. One of theſe cavities he found to be about 4000 miles deep and many times as wide. Some objections were made to this doctrine by M. De la Laude in the Memoirs of the French Academy for the year 1776, which however have been ably anſwered by Profeſſor Wilſon in reply in the Philoſ. Tranſ, for 1783. Keil obſerves, in his Aſtronomical Lectures, p. 44, ‘We frequently ſee ſpots in the ſun which are larger and broader not only than Europe or Africa, but which even equal, if they do not exceed, the ſurface of the whole terraqueous globe.’ Now that theſe cavities are made in the ſun's body by a proceſs of nature ſimilar to our earthquakes does not ſeem improbable on ſeveral accounts. 1. Becauſe from this diſcovery of Dr. Wilſon it appears that the internal parts of the ſun are not in a ſtate of inflammation or of ejecting light, like the external part or luminous ocean which covers it; and hence that a greater degree of heat or inflammation and conſequent expanſion or exploſion may occaſionally be produced in its internal or dark nucleus. 2. Becauſe the ſolar ſpots or cavities are frequently increaſed or diminiſhed in ſize. 3. New ones are often produced. 4. And old ones vaniſh. 5. Becauſe there are brighter or more luminous parts of the ſun's diſk, called faculae by Scheiner and Hevelius, which would ſeem to be volcanos in the ſun, or, as Dr. Wilſon calls them, ‘eructations of matter more luminous than that which covers the ſun's ſurface.’ 6. To which may be added that all the planets added together with their ſatellites do not amount to more than one ſix hundred and fiftieth part of the maſs of the ſun according to Sir Iſaac Newton.
Now if it could be ſuppoſed that the planets were originally thrown out of the ſun by larger ſun-quakes than thoſe frequent ones which occaſion theſe ſpots or excavations above-mentioned, what would happen? I. According to the obſervations and opinion of Mr. Herſchel the ſun itſelf and all its planets are moving forwards round ſome other centre with an unknown velocity, which may be of opake matter correſponding with the very antient and general idea of a chaos. Whence if a ponderous planet, as Saturn, could be ſuppoſed to be projected from the ſun by an exploſion, the motion of the ſun itſelf might be at the ſame time diſturbed in ſuch a manner as to prevent the planet from falling again into it. 2. As the ſun revolves round its own axis its form muſt be that of an oblate ſpheroid like the earth, and therefore a body projected from its ſurface perpendicularly upwards from that ſurface would not riſe perpendicularly from the ſun's centre, unleſs it happened to be projected exactly from either of its poles or [Page 30] from its equator. Whence it may not be neceſſary that a planet if thus projected from the ſun by exploſion ſhould again fall into the ſun. 3. They would part from the ſun's ſurface with the velocity with which that ſurface was moving, and with the velocity acquired by the exploſion, and would therefore move round the ſun in the ſame direction in which the ſun rotates on its axis, and perform eliptic orbits. 4. All the planets would move the ſame way round the ſun, from this firſt motion acquired at leaving its ſurface, but their orbits would be inclined to each other according to the diſtance of the part, where they were thrown out, from the ſun's equator. Hence thoſe which were ejected near the ſun's equator would have orbits but little inclined to each other, as the primary planets; the plain of all whoſe orbits are inclined but ſeven degrees and a half from each other. Others which were ejected near the ſun's poles would have much more eccentric orbits, as they would partake ſo much leſs of the ſun's rotatory motion at the time they parted from his ſurface, and would therefore be carried further from the ſun by the velocity they had gained by the exploſion which ejected them, and become comets. 5. They would all obey the ſame laws of motion in their revolutions round the ſun; this has been determined by aſtronomers, who have demonſtrated that they move through equal areas in equal times. 6. As their annual periods would depend on the height they roſe by the exploſion, theſe would differ in them all. 7. As their diurnal revolutions would depend on one ſide of the exploded matter adhering more than the other at the time it was torn off by the exploſion, theſe would alſo differ in the different planets, and not bear any proportion to their annual periods. Now as all theſe circumſtances coincide with the known laws of the planetary ſyſtem, they ſerve to ſtrengthen this conjecture.
This coincidence of ſuch a variety of circumſtances induced M. de Buffon to ſuppoſe that the planets were all ſtruck off from the ſun's ſurface by the impact of a large comet, ſuch as approached ſo near the ſun's diſk, and with ſuch amazing velocity, in the year 1680, and is expected to return in 2255. But Mr. Buffon did not recollect that theſe comets themſelves are only planets with more eccentric orbits, and that therefore it muſt be aſked, what had previouſly ſtruck off theſe comets from the ſun's body? 2. That if all theſe planets were ſtruck off from the ſun at the ſame time, they muſt have been ſo near as to have attracted each other and have formed one maſs: 3. That we ſhall want new cauſes for ſeparating the ſecondary planets from the primary ones, and muſt therefore look out for ſome other agent, as it does not appear how the impulſe of a comet could have made one planet roll round another at the time they both of them were driven off from the ſurface of the ſun.
If it ſhould be aſked, why new planets are not frequently ejected from the ſun? it may be anſwered, that after many large earthquakes many vents are left for the elaſtic vapours to eſcape, and hence, by the preſent appearance of the ſurface of our earth, earthquakes prodigiouſly larger than any recorded in hiſtory have exiſted; the ſame circumſtances may have affected the ſun, on whoſe ſurface there are appearances of volcanos, as deſcribed above. Add to this, that ſome of the comets, and even the georgium ſidus, may, for ought we know to the contrary, have been emitted from the ſun in more [Page 31] modern days, and have been diverted from their courſe, and thus prevented from returning into the ſun, by their approach to ſome of the older planets, which is ſomewhat countenanced by the opinion ſeveral philoſophers have maintained, that the quantity of matter of the ſun has decreaſed. Dr. Halley obſerved, that by comparing the proportion which the periodical time of the moon bore to that of the ſun in former times, with the proportion between them at preſent, that the moon is found to be ſomewhat accelerated in reſpect to the ſun. Pemberton's View of Sir Iſaac Newton, p. 247. And ſo large is the body of this mighty luminary, that all the planets thus thrown out of it would make ſcarcely any perceptible diminution of it, as mentioned above. The cavity mentioned above, as meaſured by Dr. Wilſon of 4000 miles in depth, not penetrating an hundredth part of the ſun's ſemi-diameter; and yet, as its width was many times greater than its depth, was large enough to contain a greater body than our terreſtrial world.
I do not mean to conceal, that from the laws of gravity unfolded by Sir Iſaac Newton, ſuppoſing the ſun to be a ſphere and to have no progreſſive motion, and not liable itſelf to be diſturbed by the ſuppoſed projection of the planets from it, that ſuch planets muſt return into the ſun. The late Rev. William Ludlam, of Leiceſter, whoſe genius never met with reward equal to its merits, in a letter to me, dated January, 1787, after having ſhewn, as mentioned above, that planets ſo projected from the ſun would return to it, adds, ‘That a body as large as the moon ſo projected, would diſturb the motion of the earth in its orbit, is certain; but the calculation of ſuch diſturbing forces is difficult. The body in ſome circumſtances might become a ſatellite, and both move round their common centre of gravity, and that centre be carried in an annual orbit round the ſun.’
There are other circumſtances which might have concurred at the time of ſuch ſuppoſed exploſions, which would render this idea not impoſſible. I. The planets might be thrown out of the ſun at the time the ſun itſelf was riſing from chaos, and be attracted by other ſuns in their vicinity riſing at the ſame time out of chaos, which would prevent them from returning into the ſun. 2. The new planet in its courſe or aſcent from the ſun, might explode and eject a ſatellite, or perhaps more than one, and thus by its courſe being affected might not return into the ſun. 3. If more planets were ejected at the ſame time from the ſun, they might attract and diſturb each others courſe at the time they left the body of the ſun, or very ſoon afterwards, when they would be ſo much nearer each other.
While Ocean wrap'd it in his azure robe.CANTO II. 1. 34.
FROM having obſerved that many of the higheſt mountains of the world conſiſt of lime-ſtone replete with ſhells, and that theſe mountains bear the marks of having been lifted up by ſubterraneous fires from the interior parts of the globe; and as lime-ſtone replete with ſhells is found at the bottom of many of our deepeſt mines ſome philoſophers have concluded that the nucleus of the earth was for many ages covered with water which was peopled with its adapted animals; that the ſhells and bones of theſe animals in a long ſeries of time produced ſolid ſtrata in the ocean ſurrounding the original nucleus.
Theſe ſtrata conſiſt of the accumulated exuviae of ſhell-fiſh, the animals periſhed age after age but their ſhells remained, and in progreſſion of time produced the amazing quantities of lime-ſtone which almoſt cover the earth. Other marine animals called coralloids raiſed walls and even mountains by the congeries of their calcareous habitations, theſe perpendicular corralline rocks make ſome parts of the Southern Ocean highly dangerous, as appears in the journals of Capt. Cook. From contemplating the immenſe ſtrata of lime-ſtone, both in reſpect to their extent and thickneſs, formed from theſe ſhells of animals, philoſophers have been led to conclude that much of the water of the ſea has been converted into calcareous earth by paſſing through their organs of digeſtion. The formation of calcareous earth ſeems more particularly to be an animal proceſs as the formation of clay belongs to the vegetable economy; thus the ſhells of crabs and other teſtaceous fiſh are annually reproduced from the mucous membrane beneath them; the ſhells of eggs are firſt a mucous membrane, and the calculi of the kidneys and thoſe found in all other parts of our ſyſtem which ſometimes contain calcareous earth, ſeem to originate from inflamed membranes; the bones themſelves conſiſt of calcareous earth united with the phoſphoric or animal acid, which may be ſeparated by diſſolving the aſhes of calcined bones in the nitrous acid; the various ſecretions of animals, as their ſaliva and urine, abound likewiſe with calcareous earth, as appears by the incruſtations about the teeth and the ſediments of urine. It is probable that animal mucus is a previous proceſs towards the formation of calcareous earth; and that all the calcareous earth in the world which is ſeen in lime-ſtones, marbles, ſpars, alabaſters, marls, (which make up the greateſt part of the earth's cruſt, as far as it has yet been penetrated,) have been formed originally by animal and vegetable bodies from the maſs of water, and that by theſe means the ſolid part of the terraqueous globe has perpetually been in an increaſing ſtate and the water perpetually in a decreaſing one.
After the mountains of ſhells and other recrements of aquatic animals were elevated above the water the upper heaps of them were gradually diſſolved by rains and dews and oozing through were either perfectly cryſtallized in ſmaller cavities and formed [Page 33] calcareous ſpar, or were imperfectly cryſtallized on the roofs of larger cavities and produced ſtalactites; or mixing with other undiſſolved ſhells beneath them formed marbles, which were more or leſs cryſtallized and more or leſs pure; or laſtly, after being diſſolved, the water was exhaled from them in ſuch a manner that the external parts became ſolid, and forming an arch prevented the internal parts from approaching each other ſo near as to become ſolid, and thus chalk was produced. I have ſpecimens of chalk formed at the root of ſeveral ſtalactites, and in their central parts; and of other ſtalactites which are hollow like quills from a ſimilar cauſe, viz. from the external part of the ſtalactite hardening firſt by its evaporation, and thus either attracting the internal diſſolved particles to the cruſt, or preventing them from approaching each other ſo as to form a ſolid body. Of theſe I ſaw many hanging from the arched roof of a cellar under the high ſtreet in Edinburgh.
If this diſſolved limeſtone met with vitriolic acid it was converted into alabaſter, parting at the ſame time with its fixable air. If it met with the fluor acid it became fluor; if with the ſiliceous acid, flint; and when mixed with clay and ſand, or either of them, acquires the name of marl. And under one or other of theſe forms compoſes a great part of the ſolid globe of the earth.
Another mode in which limeſtone appears is in the form of round granulated particles, but ſlightly cohering together; of this kind a bed extends over Lincoln heath, perhaps twenty miles long by ten wide. The form of this calcareous ſand, its angles having been rubbed off, and the flatneſs of its bed, evinces that that part of the country was ſo formed under water, the particles of ſand having thus been rounded, like all other rounded pebbles. This round form of calcareous ſand and of other larger pebbles is produced under water, partly by their being more or leſs ſoluble in water, and hence the angular parts become diſſolved, firſt, by their expoſing a larger ſurface to the action of the menſtruum, and ſecondly, from their attrition againſt each other by the ſtreams or tides, for a great length of time, ſucceſſively as they were collected, and perhaps when ſome of them had not acquired their hardeſt ſtate.
This calcareous ſand has generally been called ketton-ſtone and believed to reſemble the ſpawn of fiſh, it has acquired a form ſo much rounder than ſiliceous ſand from its being of ſo much ſofter a texture and alſo much more ſoluble in water. There are other ſoft calcareous ſtones called tupha which are depoſited from water on moſſes, as at Matlock, from which moſs it is probable the water may receive ſomething which induces it the readier to part with its earth.
In ſome lime-ſtones the living animals ſeem to have been buried as well as their ſhells during ſome great convulſion of nature, theſe ſhells contain a black coaly ſubſtance within them, in others ſome phlogiſton or volatile alcali from the bodies of the dead animals remains mixed with the ſtone, which is then called liver-ſtone as it emits a ſulphurous ſmell on being ſtruck, and there is a ſtratum about ſix inches thick extends a conſiderable way over the iron ore at Wingerworth near Cheſterfield in Derbyſhire which ſeems evidently to have been formed from the ſhells of freſh-water muſcles
[Page 34] There is however another ſource of calcareous earth beſides the aquatic one above deſcribed and that is from the recrements of land animals and vegetables as found in marls, which conſiſt of various mixtures of calcareous earth, ſand, and clay, all of them perhaps principally from vegetable origin.
Dr. Hutton is of opinion that the rocks of marble have been ſoftened by fire into a fluid maſs, which he thinks under immenſe preſſure might be done without the eſcape of their carbonic acid or fixed air. Edinb. Tranſact. Vol. I. If this ingenious idea be allowed it might account for the purity of ſome white marbles, as during their fluid ſtate there might be time for their partial impurities, whether from the bodies of the animals which produced the ſhells or from other extraneous matter, either to ſublime to the uppermoſt part of the ſtratum or to ſubſide to the lowermoſt part of it. As a confirmation of this theory of Dr. Hutton's it may be added that ſome calcareous ſtones are found mixed with lime, and have thence loſt a part of their fixed air or carbonic gas, as the bath-ſtone, and on that account hardens on being expoſed to the air, and mixed with ſulphur produces calcareous liver of ſulphur. Falconer on Bathwater. Vol. I. p. 156. and p. 257. Mr. Monnet found lime in powder in the mountains of Auvergne, and ſuſpected it of volcanic origin. Kirwan's Min. p. 22.
Gnomes! you then taught tranſuding dews to paſsThrough time-fallen woods, and root-inwove moraſs.CANTO II. l. 113.
WHERE woods have repeatedly grown and periſhed moraſſes are in proceſs of time produced, and by their long roots fill up the interſtices till the whole becomes for many yards deep a maſs of vegetation. This fact is curiouſly verified by an account given many years ago by the Earl of Cromartie, of which the following is a ſhort abſtract.
In the year 1651 the EARL OF CROMARTIE being then nineteen years of age ſaw a plain in the pariſh of Lockburn covered over with a firm ſtanding wood, which was ſo old that not only the trees had no green leaves upon them but the bark was totally thrown off, which he was there informed by the old countrymen was the univerſal manner in which fir-woods terminated, and that in twenty or thirty years the trees would caſt themſelves up by the roots. About fifteen years after he had occaſion to travel the ſame way and obſerved that there was not a tree nor the appearance of a root of any of them; but in their place the whole plain where the wood ſtood was [Page 35] covered with a flat green moſs or moraſs, and on aſking the country people what was become of the wood he was informed that no one had been at the trouble to carry it away, but that it had all been overturned by the wind, that the trees lay thick over each other, and that the moſs or bog had overgrown the whole timber, which they added was occaſioned by the moiſture which came down from the high hills above it and ſtagnated upon the plain, and that nobody could yet paſs over it, which however his Lordſhip was ſo incautious as to attempt and ſlipt up to the arm-pits. Before the year 1699 that whole piece of ground was become a ſolid moſs wherein the peaſants then dug turf or peat, which however was not yet of the beſt ſort. Philos. Trans. No. 330. Abridg. Vol. V. p. 272.
Moraſſes in great length of time undergo variety of changes, firſt by elutriation, and afterwards by fermentation, and the conſequent heat. 1. By water perpetually oozing through them the moſt ſoluble parts are firſt waſhed away, as the eſſential ſalts, theſe together with the ſalts from animal recrements are carried down the rivers into the ſea, where all of them ſeem to decompoſe each other except the marine ſalt. Hence the aſhes of peat contain little or no vegetable alcali and are not uſed in the countries, where peat conſtitutes the fuel of the lower people, for the purpoſe of waſhing linen. The ſecond thing which is always ſeen oozing from moraſſes is iron in ſolution, which produces chalybeate ſprings, from whence depoſitions of ochre and variety of iron ores. The third elutriation ſeems to conſiſt of vegetable acid, which by means unknown appears to be converted into all other acids. 1. Into marine and nitrous acids as mentioned above. 2. Into vitriolic acid which is found in ſome moraſſes ſo plentifully as to preſerve the bodies of animals from putrefaction which have been buried in them, and this acid carried away by rain and dews and meeting with calcareous earth produces gypſum or alabaſter, with clay it produces alum, and deprived of its vital air produces ſulphur. 3. Fluor acid which being waſhed away and meeting with calcareous earth produces fluor or cubic ſpar. 4. The ſiliceous acid which ſeems to have been disſeminated in great quantity either by ſolution in water or by ſolution in air, and appears to have produced the ſand in the ſea uniting with calcareous earth previouſly diſſolved in that element, from which were afterwards formed ſome of the grit-ſtone rocks by means of a ſiliceous or calcareous cement. By its union with the calcareous earth of the moraſs other ſtrata of ſiliceous ſand have been produced; and by the mixture of this with clay and lime aroſe the beds of marl.
In other circumſtances, probably where leſs moiſture has prevailed, moraſſes ſeem to have undergone a fermentation, as other vegetable matter, new hay for inſtance is liable to do from the great quantity of ſugar it contains. From the great heat thus produced in the lower parts of immenſe beds of moraſs the phlogiſtic part, or oil, or aſphaltum, becomes diſtilled, and riſing into higher ſtrata becomes again condenſed forming coalbeds of greater or leſs purity according to their greater or leſs quantity of inflammable matter; at the ſame time the clay beds become purer or leſs ſo, as the phlogiſtic part is more or leſs completely exhaled from them. Though coal and clay are frequently produced in this manner, yet I have no doubt, but that they are likewiſe often produced by [Page 36] elutriation; in ſituations on declivities the clay is waſhed away down into the valleys, and the phlogiſtic part or coal left behind; this circumſtance is ſeen in many valleys near the beds of rivers, which are covered recently by a whitiſh impure clay, called waterclay. See note XIX. XX. and XXIII.
LORD CROMARTIE has furniſhed another curious obſervation on moraſſes in the paper above referred to. In a moſs near the town of Eglin in Murray, though there is no river or water which communicates with the moſs, yet for three or four feet of depth in the moſs there are little ſhell-fiſh reſembling oyſters with living fiſh in them in great quantities, though no ſuch fiſh are found in the adjacent rivers, nor even in the water pits in the moſs, but only in the ſolid ſubſtance of the moſs. This curious fact not only accounts for the ſhells ſometimes found on the ſurface of coals, and in the clay above them; but alſo for a thin ſtratum of ſhells which ſometimes exiſts over iron-ore.
Cold waves, immerged, the glowing maſs congeal,And turn to adamant the hiſſing Steel.CANTO II. l. 191.
AS iron is formed near the ſurface of the earth, it becomes expoſed to ſtreams of water and of air more than moſt other metallic bodies, and thence becomes combined with oxygene, or vital air, and appears very frequently in its calciform ſtate, as in variety of ochres. Manganeſe, and zinc, and ſometimes lead, are alſo found near the ſurface of the earth, and on that account become combined with vital air and are exhibited in their calciform ſtate.
The avidity with which iron unites with oxygene, or vital air, in which proceſs much heat is given out from the combining materials, is ſhewn by a curious experiment of M. Ingenhouz. A fine iron wire twiſted ſpirally is fixed to a cork, on the point of the ſpire is fixed a match made of agaric dipped in ſolution of nitre; the match is then ignited, and the wire with the cork put immediately into a bottle full of vital air, the match firſt burns vividly, and the iron ſoon takes fire and conſumes with brilliant ſparks till it is reduced to ſmall brittle globules, gaining an addition of about one third of its weight by its union with vital air. Annales de Chymic. Traité de Chimie, per Lavoiſier, c. iii.
It is probably owing to a total deprivation of vital air which it holds with ſo great avidity, that iron on being kept many hours or days in ignited charcoal becomes converted into ſteel, and thence acquires the faculty of being welded when red hot long before it melts, and alſo the power of becoming hard when immerſed in cold water; both which I ſuppoſe depend on the ſame cauſe, that is, on its being a worſe conductor of heat than other metals; and hence the ſurface both acquires heat much ſooner, and loſes it much ſooner, than the internal parts of it, in this-circumſtance reſembling glaſs.
When ſteel is made very hot, and ſuddenly immerged in very cold water, and moved about in it, the ſurface of the ſteel becomes cooled firſt, and thus producing a kind of caſe or arch over the internal part, prevents that internal part from contracting quite ſo much as it otherwiſe would do, whence it becomes brittler and harder, like the glaſsdrops called Prince Rupert's drops, which are made by dropping melted glaſs into cold water. This idea is countenanced by the circumſtance that hardened ſteel is ſpecifically lighter than ſteel which is more gradually cooled. (Nicholſon's Chemiſtry, p. 313.) Why the brittleneſs and hardneſs of ſteel or glaſs ſhould keep pace or be companions to each other may be difficult to conceive.
When a ſteel ſpring is forcibly bent till it break, it requires leſs power to bend it through the firſt inch than the ſecond, and leſs through the ſecond than the third; the ſame I ſuppoſe to happen if a wire be diſtended till it break by hanging weights to it; this ſhews that the particles may be forced from each other to a ſmall diſtance by leſs power, than is neceſſary to make them recede to a greater diſtance; in this circumſtance perhaps the attraction of coheſion differs from that of gravitation, which exerts its power inverſely as the ſquares of the diſtance. Hence it appears that is the innermoſt particles of a ſteel bar, by cooling the external ſurface firſt, are kept from approaching each other ſo nearly as they otherwiſe would do, that they become in the ſituation of the particles on the convex ſide of a bent ſpring, and can not be forced further from each other except by a greater power than would have been neceſſary to have made them recede thus far. And ſecondly, that if they be forced a little further from each other they ſeparate; this may be exemplified by laying two magnetic needles parallel to each other, the contrary poles together, then drawing them longitudinally from each other, they will ſlide with ſmall force till they begin to ſeparate, and will then require a ſtronger force to really ſeparate them. Hence it appears, that hardneſs and brittleneſs depend on the ſame circumſtance, that the particles are removed to a greater diſtance from each other and thus reſiſt any power more forcibly which is applied to diſplace them further, this conſtitutes hardneſs. And ſecondly, if they are diſplaced by ſuch applied force they immediately ſeparate, and this conſtitutes brittleneſs.
Steel may be thus rendered too brittle for many purpoſes, on which account artiſts have means of ſoftening it again, by expoſing it to certain degrees of heat, for the conſtruction of different kinds of tools, which is called tempering it. Some artiſts plunge large tools in very cold water as ſoon as they are compleatly ignited, and moving it about, [Page 38] take it out as ſoon as it ceaſes to be luminous beneath the water; it is then rubbed quickly with a file or on ſand to clean the ſurface, the heat which the metal ſtill retains ſoon begins to produce a ſucceſſion of colours; if a hard temper be required, the piece is dipped again and ſtirred about in cold water as ſoon as the yellow tinge appears, if it be cooled when the purple tinge appears it becomes fit for gravers' tools uſed in working upon metals; if cooled while blue it is proper for ſprings. Nicholſon's Chemiſtry, p. 313. Keir's Chemical Dictionary.
The recent production of iron is evinced from the chalybeate waters which flow from moraſſes which lie upon gravel-beds, and which muſt therefore have produced iron after thoſe gravel-beds were raiſed out of the ſea. On the ſouth ſide of the road between Cheadle and Okeymoor in Staffordſhire, yellow ſtains of iron are ſeen to penetrate the gravel from a thin moraſs on its ſurface. There is a fiſſure eight or ten feet wide, in a gravel-bed on the eaſtern ſide of the hollow road aſcending the hill about a mile from Trentham in Staffordſhire, leading toward Drayton in Shropſhire, which fiſſure is filled up with nodules of iron-ore. A bank of ſods is now raiſed againſt this fiſſure to prevent the looſe iron nodules from falling into the turnpike road, and thus this natural curioſity is at preſent concealed from travellers. A ſimilar fiſſure in a bed of marl, and filled up with iron nodules and with ſome large pieces of flint, is ſeen on the eaſtern ſide of the hollow road aſcending the hill from the turnpike houſe about a mile from Derby in the road towards Burton. And another ſuch fiſſure filled with iron nodes, appears about half a mile from Newton-Solney in Derbyſhire, in the road to Burton, near the ſummit of the hill. Theſe collections of iron and of flint muſt have been produced poſterior to the elevation of all thoſe hills, and were thence evidently of vegetable or animal origin. To which ſhould be added, that iron is found in general in beds either near the ſurface of the earth, or ſtratified with clay coals or argillaceous grit, which are themſelves productions of the modern world, that is, from the recrements of vegetables and air-breathing animals.
Not only iron but mangancſe, calamy, and even copper and lead appear in ſome inſtances to have been of recent production. Iron and manganeſe are detected in all vegetable productions, and it is probable other metallic bodies might be found to exiſt in vegetable or animal matters, if we had teſts to detect them in very minute quantities. Manganeſe and calamy are found in beds like iron near the ſurface of the earth, and in a calciform ſtate, which countenances their modern production. The recent production of calamy, one of the ores of zinc, appears from its frequently incruſting calcareous ſpar in its deſcent from the ſurface of the earth into the uppermoſt fiſſures of the limeſtone mountains of Derbyſhire. That the calamy has been carried by its ſolution or diffuſion in water into theſe cavities, and not by its aſcent from below in form of ſteam, is evinced from its not only forming a cruſt over the dogtooth ſpar, but by its afterwards diſſolving or deſtroying the ſparry cryſtal. I have ſpecimens of calamy in the form of dogtooth ſpar, two inches high, which are hollow, and ſtand half an inch above the diminiſhed [Page 39] ſparry cryſtal on which they were formed, like a ſheath a great deal too big for it; this ſeems to ſhew, that this proceſs was carried on in water, otherwiſe after the calamy had incruſted its ſpar, and diſſolved its ſurface, ſo as to form a hollow cavern over it, it could not act further upon it except by the interpoſition of ſome medium. As theſe ſpars and calamy are formed in the fiſſures of mountains they muſt both have been formed after the elevation of thoſe mountains.
In reſpect to the recent production of copper, it was before obſerved in note on Canto II. l. 394, that the ſummit of the grit-ſtone mountain at Hawkſtone in Shropſhire, is tinged with copper, which from the appearance of the blue ſtains ſeems to have deſcended to the parts of the rock beneath. I have a calciform ore of copper conſiſting of the hollow cruſts of cubic cells, which has evidently been formed on cryſtals of fluor, which it has eroded in the ſame manner as the calamy erodes the calcareous cryſtals, from whence may be deduced in the ſame manner, the aqueous ſolution or diffuſion, as well as the recent production of this calciform ore of copper.
Lead in ſmall quantities is ſometimes found in the fiſſures of coal-beds, which fisſures are previouſly covered with ſpar; and ſometimes in nodules of iron-ore. Of the former I have a ſpecimen from near Caulk in Derbyſhire, and of the latter from Colebrook Dale in Shropſhire. Though all theſe facts ſhew that ſome metallic bodies are formed from vegetable or animal recrements, as iron, and perhaps manganeſe and calamy, all which are found near the ſurface of the earth; yet as the other metals are found only in fiſſures of rocks, which penetrate to unknown depths, they may be wholly or in part produced by aſcending ſteams from ſubterraneous fires, as mentioned in note on Canto II. l. 394.
Over ſome lime works at Walſall in Staffordſhire, I obſerved ſome years ago a ſtratum of iron earth about ſix inches thick, full of very large cavities; theſe cavities were evidently produced when the material paſſed from a ſemifluid ſtate into a ſolid one; as the frit of the potters, or a mixture of clay and water is liable to crack in drying; which is owing to the further contraction of the internal part, after the cruſt is become hard. Theſe hollows are liable to receive extraneous matter, as I believe gypſum, and ſometimes ſpar, and even lead; a curious ſpecimen of the laſt was preſented to me by Mr. Darby of Colebrook Dale, which contains in its cavity ſome ounces of lead-ore. But there are other ſeptaria of iron-ſtone which ſeem to have had a very different origin, their cavities having been formed in cooling or congealing from an ignited ſtate, as is ingeniouſly deduced by Dr. Hutton from their internal ſtruture. Edinb. Tranſact. Vol. I. p. 246. The volcanic origin of theſe curious ſeptaria appears to me to be further evinced from their form and the places where they are found. They conſiſt of oblate ſpheroids and are found in many parts of the earth totally detached from the beds in which they lie, as at Eaſt Lothian in Scotland. Two of theſe, which now lie before me, were found with many others immerſed in argillaceous ſhale or ſhiver, ſurrounded by broken limeſtone mountains at Bradbourn near Aſhbourn in Derbyſhire, and were preſented to [Page 40] me by Mr. Buxton, a gentleman of that town. One of theſe is about fifteen inches in its equatorial diameter, and about ſix inches in its polar one, and contains beautiful ſtarlike ſeptaria incruſted and in part filled with calcareous ſpar. The other is about eight inches in its equatorial diameter, and about four inches in its polar diameter, and is quite ſolid, but ſhews on its internal ſurface marks of different colours, as if a beginning ſeparation had taken place. Now as theſe ſeptaria contain fifty per cent, of iron, according to Dr. Hutton, they would ſoften or melt into a ſemifluid globule by ſubterraneous fire by leſs heat than the limeſtone in their vicinity; and if they were ejected through a hole or fiſſure would gain a circular motion along with their progreſſive one by their greater friction or adheſion to one ſide of the hole. This whirling motion would produce the oblate ſpheroidical form which they poſſeſs, and which as far as I know can not in any other way be accounted for. They would then harden in the air as they roſe into the colder parts of the atmoſphere; and as they deſcended into ſo ſoft a material as ſhale or ſhiver, their forms would not be injured in their fall; and their preſence in materials ſo different from themſelves becomes accounted for.
About the tropics of the large ſeptarium above mentioned, are circular eminent lines, ſuch as might have been left is it had been coarſely turned in a lathe. Theſe lines ſeem to conſiſt of a fluid matter, which ſeems to have exſuded in circular zones, as their edges appear blunted or retracted; and the ſeptarium ſeems to have ſplit eaſier in ſuch ſections parallel to its equator. Now as the cruſt would firſt begin to cool and harden after its ejection in a ſemifluid ſtate, and the equatorial diameter would become gradually enlarged as it roſe in the air; the internal parts being ſofter would ſlide beneath the polar cruſt, which might crack and permit part of the ſemifluid to exſude, and it is probable the adheſion would thus become leſs in ſections parallel to the equator. Which further confirms this idea of the production of theſe curious ſeptaria. A new-caſt cannon ball red-hot with its cruſt only ſolid, if it were ſhot into the air would propably burſt in its paſſage; as it would conſiſt of a more fluid material than theſe ſeptaria; and thus by diſcharging a ſhower of liquid iron would produce more dreadful combuſtion, if uſed in war, than could be effected by a ball, which had been cooled and was heated again: ſince in the latter caſe the ball could not have its internal parts made hotter than the cruſt of it, without firſt looſing its form.
Tranſmute to glittering flints her chalky lands,Or ſink on Ocean's bed in countleſs ſands.CANTO II. l. 217.
THE great maſſes of ſiliceous ſand which lie in rocks upon the beds of limeſtone, or which are ſtratified with clay, coal, and iron-ore, are evidently produced in the decompoſition of vegetable or animal matters, as explained in the note on moraſſes. Hence the impreſſions of vegetable roots and even whole trees are often found in ſand-ſtone, as well as in coals and iron-ore. In theſe ſand-rocks both the ſiliceous acid and the calcareous baſe ſeem to be produced from the materials of the moraſs; for though the prefence of a ſiliceous acid and of a calcareous baſe have not yet been ſeparately exhibited from flints, yet from the analogy of flint to fluor, and gypſum, and marble, and from the converſion of the latter into flint, there can be little doubt of their exiſtence.
Theſe ſiliceous ſand-rocks are either held together by a ſiliceous cement, or have a greater or leſs portion of clay in them, which in ſome acts as a cement to the ſiliceous cryſtals, but in others is in ſuch great abundance that in burning them they become an imperfect porcelain and are then uſed to repair the roads, as at Cheſterfield in Derbyſhire; theſe are called argillaceous grit by Mr. Kirwan. In other places a calcareous matter cements the cryſtals together; and in other places the ſiliceous cryſtals lie in looſe ſtrata under the marl in the form of white ſand; as at Normington about a mile from Derby.
The loweſt beds of ſiliceous ſand-ſtone produced from moraſſes ſeem to obtain their acid from the moraſs, and their calcareous baſe from the limeſtone on which it reſts. Theſe beds poſſeſs a ſiliceous cement, and from their greater purity and hardneſs are uſed for courſe grinding-ſtones and ſcyth ſtones, and are ſituated on the edges of limeſtone countries, having loſt the other ſtrata of coals, or clay, or iron, which were originally produced above them. Such are the ſand-rocks incumbent on limeſtone near Matlock in Derbyſhire. As theſe ſiliceous ſand-rocks contain no marine productions ſcattered amongſt them, they appear to have been elevated, torn to pieces, and many fragments of them ſcattered over the adjacent country by exploſions, from fires within the moraſs from which they have been formed; and which diſſipated every thing inflammable above and beneath them, except ſome ſtains of iron, with which they are in ſome places ſpotted. If theſe ſand-rocks had been accumulated beneath the ſea, and elevated along with the beds of limeſtone on which they reſt, ſome veſtiges of marine ſhells either in their ſiliceous or calcareous ſtate muſt have been diſcerned amongſt them.
In many of theſe ſand-rocks are found the impreſſions of vegetable roots, which ſeem to have been the moſt unchangeable parts of the plant, as ſhells and ſhark's teeth are found in chalk-beds from their being the moſt unchangeable parts of the animal. In other inſtances the wood itſelf is penetrated, and whole trees converted into flint; ſpecimens of which I have by me, from near Covenery, and from a gravel-pit in Shropſhire near Child's Archal in the road to Drayton. Other poliſhed ſpecimens of vegetable flints abound in the cabinets of the curious, which evidently ſhew the concentric circles of woody fibres, and their interſtices filled with whiter ſiliceous matter, with the branching off of the knots when cut horizontally, and the parallel lines of wood when cut longitudinally, with uncommon beauty and variety. Of theſe I poſſeſs ſome beautiful ſpecimens, which were preſented to me by the Earl of Uxbridge.
The colours of theſe ſiliceous vegetables are generally brown, from the iron, I ſuppoſe, or manganeſe, which induced them to cryſtallize or to fuſe more eaſily. Some of the cracks of the wood in drying are filled with white flint or calcedony, and others of them remain hollow, lined with innumerable ſmall cryſtals tinged with iron, which I ſuppoſe had a ſhare in converting their calcareous matter into ſiliceous cryſtals, becauſe the cryſtals called Peak-diamonds are always found bedded in an ochreous earth; and thoſe called Briſtol-ſtones are ſituated on limeſtone coloured with iron. Mr. F. French preſented me with a congeries of ſiliceous cryſtals, which he gathered on the crater (as he ſuppoſes) of an extinguiſhed volcano at Cromach Water in Cumberland. The cryſtals are about an inch high in the ſhape of dogtooth or calcareous ſpar, covered with a dark ferruginous matter. The bed on which they reſt is about an inch in thickneſs, and is ſtained with iron on its underſurface. This curious foſſil ſhews the tranſmutation of calcareous earth into ſiliceous, as much as the ſiliceous ſhells which abound in the cabinets of the curious. There may ſometime be diſcovered in this age of ſcience, a method of thus impregnating wood with liquid flint, which would produce pillars for the ſupport, and tiles for the covering of houſes, which would be uninflammable and endure as long as the earth beneath them.
That ſome ſiliceous productions have been in a fluid ſtate without much heat at the time of their formation appears from the vegetable flints above deſcribed not having quite loſt their organized appearance; from ſhells, and coralloids, and entrochi being converted into flint without looſing their form; from the baſon of calcedony round Gieſar in Iceland; and from the experiment of Mr. Bergman, who obtained thirteen regular formed cryſtals by ſuffering the powder of quartz to remain in a veſſel with fluor acid for two years; theſe cryſtals were about the ſize of ſmall peas, and were not ſo hard as quartz. Opuſc. de Terrâ Siliceâ, p. 33. Mr. Achard procured both calcareous and ſiliceous cryſtals, one from calcareous earth, and the other from the earth of alum, both diſſolved in water impregnated with fixed air; the water filtrating very ſlowly through a porous bottom of baked clay. See Journal de Phyſique, for January, 1778.
In ſmall cavities of theſe ſand-rocks, I am informed, the beautiful ſiliceous nodules are found which are called Scot's-pebbles; and which on being cut in different directions take the names of agates, onyxes, ſardonyxes, &c. according to the colours of the lines or ſtrata which they exhibit. Some of the nodules are hollow and filled with cryſtals, others have a nucleus of leſs compact ſiliceous matter which is generally white, ſurrounded with many concentric ſtrata coloured with iron, and other alternate ſtrata of white agate or calcedony, ſometimes to the number of thirty.
I think theſe nodules bear evident marks of their having been in perfect fuſion by either heat alone, or by water and heat, under great preſſure, according to the ingenious theory of Dr. Hutton; but I do not imagine, that they were injected into cavities from materials from without, but that ſome vegetables or parts of vegetables containing more iron or manganeſe than others, facilitated the compleat fuſion, thus deſtroying the veſtiges of vegetable organization, which were conſpicuous in the ſiliceous trees above mentioned. Some of theſe nodules being hollow and lined with cryſtals, and others containing a nucleus of white ſiliceous matter of a looſer texture, ſhew they were compoſed of the materials then exiſting in the cavity; which conſiſting before of looſe ſand, muſt take up leſs ſpace when fuſed into a ſolid maſs.
Theſe ſiliceous nodules reſemble the nodules of iron-ſtone mentioned in note on Canto II. l. 179, in reſpect to their poſſeſſing a great number of concentric ſpheres coloured generally with iron, but they differ in this circumſtance, that the concentric ſpheres generally obey the form of the external cruſt, and in their not poſſeſſing a chalybeate nucleus. The ſtalactites formed on the roofs of caverns are often coloured in concentric ſtrata, by their coats being ſpread over each other at different times; and ſome of them, as the cupreous ones, poſſeſs great beauty from this formation; but as theſe are neceſſarily more or leſs of a cylindrical or conic form, the nodules or globular flints above deſcribed cannot have been conſtructed in this manner. To what law of nature then is to be referred the production of ſuch numerous concentric ſpheres? I ſuſpect to the law of congelation.
When ſalt and water are expoſed to ſevere froſty air, the ſalt is ſaid to be precipitated as the water freezes; that is, as the heat, in which it was diſſolved, is withdrawn; where the experiment is tried in a bowl or baſon, this may be true, as the ſurface freezes firſt, and the ſalt is found at the bottom. But in a fluid expoſed in a thin phial, I found by experiment, that the extraneous matter previouſly diſſolved by the heat in the mixture was not ſimply ſet at liberty to ſubſide, but was detruded or puſhed backward as the ice was produced. The experiment was this: about two ounces of a ſolution of blue vitriol were accidentally frozen in a thin phial, the glaſs was cracked and fallen to pieces, the ice was diſſolved, and I found a pillar of blue vitriol ſtanding erect on the bottom of the broken bottle. Nor is this power of congelation more extraordinary, than that by its powerful and ſudden expanſion it ſhould burſt iron ſhells and coehorns, or throw [Page 44] out the plugs with which the water was ſecured in them above one hundred and thirty yards, according to the experiments at Quebec by Major Williams. Edinb. Tranſact. Vol. II. p. 23.
In ſome ſiliceous nodules which now lie before me, the external cruſt for about the tenth of an inch conſiſts of white agate, in others it is much thinner, and in ſome much thicker; correſponding with this cruſt there are from twenty to thirty ſuperincumbent ſtrata, of alternately darker and lighter colour; whence it appears, that the external cruſt as it cooled or froze, propelled from it the iron or manganeſe which was diſſolved in it; this receded till it had formed an arch or vault ſtrong enough to reſiſt its further protruſion; then the next inner ſphere or ſtratum as it cooled or froze, propelled forwards its colouring matter in the ſame manner, till another arch or ſphere produced ſufficient reſiſtance to this frigorific expulſion. Some of them have detruded their colouring matter quite to the centre, the rings continuing to become darker as they are nearer it; in others the chalybeate arch ſeems to have ſtopped half an inch from the centre, and become thicker by having attracted to itſelf the irony matter from the white nucleus, owing probably to its cooling leſs precipitately in the central parts than at the ſurface of the pebble.
A ſimilar detruſion of a marly matter in circular arches or vaults obtains in the ſalt mines in Cheſhire; from whence Dr. Hutton very ingeniouſly concludes, that the ſalt muſt have been liquified by heat; which would ſeem to be be much confirmed by the above theory. Edinb. Tranſact. Vol. I. p. 244.
I cannot conclude this account of Scots-pebbles without obſerving that ſome of them on being ſawed longitudinally aſunder, ſeem ſtill to poſſeſs ſome veſtiges of the cylindrical organization of vegetables; others poſſeſs a nucleus of white agate much reſembling ſome bulbous roots with their concentric coats, or the knots in elm-roots or crab-trees; ſome of theſe I ſuppoſe were formed in the manner above explained, during the congelation of maſſes of melted flint and iron; others may have been formed from a vegetable nucleus, and retain ſome veſtiges of the organization of the plant.
The great abundance of ſiliceous ſand at the bottom of the ocean may in part be waſhed down from the ſiliceous rocks above deſcribed, but in general I ſuppoſe it derives its acid only from the vegetable and animal matter of moraſſes, which is carried down by floods or by the atmoſphere, and becomes united in the ſea with its calcareous baſe from ſhells and coralloids, and thus aſſumes its cryſtalline form at the bottom of the ocean, and is there intermixed with gravel or other matters waſhed from the mountains in its vicinity.
The rocks of marble are often alternately intermixed with ſtrata of chert, or coarſe flint, and this in beds from one to three feet thick, as at Ilam and Matlock, or of leſs than the tenth of an inch in thickneſs, as a mile or two from Bakewell in the road to [Page 45] Buxton. It is difficult to conceive in what manner ten or twenty ſtrata of either limeſtone or flint, of different ſhades of white and black, could be laid quite regularly over each other from ſediments or precipitations from the ſea; it appears to me much eaſier to comprehend, by ſuppoſing with Dr. Hutton, that both the ſolid rocks of marble and the flint had been fuſed by great heat, (or by heat and water,) under immenſe preſſure; by its cooling or congelating the colouring matter might be detruded, and form parallel or curvilinean ſtrata, as above explained.
The colouring matter both of limeſtone and flint was probably owing to the fleſh of peculiar animals, as well as the ſiliceous acid, which converted ſome of the limeſtone into flint; or to ſome ſtrata of ſhell-fiſh having been overwhelmed when alive with new materials, while others dying in their natural ſituations would loſe their fleſhy parts, either by its putrid ſolution in the water or by its being eaten by other ſea-inſects. I have ſome calcareous foſſil ſhells which contain a black coaly matter in them, which was evidently the body of the animal, and others of the ſame kind filled with ſpar inſtead of it. The Labradore ſtone has I ſuppoſe its colours from the nacre or mother-pearl ſhells, from which it was probably produced. And there is a ſtratum of calcareous matter about ſix or eight inches thick at Wingerworth in Derbyſhire over the iron-beds, which is replete with ſhells of freſh-water muſcles, and evidently obtains its dark colour from them, as mentioned in note XVI. Many nodules of flint reſemble in colour as well as in form the ſhell of the echinus or ſea-urchin; others reſemble ſome coralloids both in form and colour; and M. Arduini found in the Monte de Pancraſio, red flints branching like corals, from whence they ſeem to have obtained both their form and their colour. Ferber's Travels in Italy, p. 42.
As the nodules of flint found in chalk-beds poſſeſs no marks of having been rounded by attrition or ſolution, I conclude that they have gained their form as well as their dark colour from the fleſh of the ſhell-fiſh from which they had their origin; but which have been ſo compleatly fuſed by heat, or heat and water, as to obliterate all veſtiges of the ſhell, in the ſame manner as the nodules of agate and onyx were produced from parts of vegetables, but which had been ſo completely fuſed as to obliterate all marks of their organization, or as many iron-nodules have obtained their form and origin from peculiar vegetables.
Some nodules in chalk-beds conſiſt of ſhells of echini filled up with chalk, the animal having been diſſolved away by putreſcence in water, or eaten by other ſea-inſects; other ſhells of echini, in which I ſuppoſe the animal's body remained, are converted into flint but ſtill retain the form of the ſhell. Others, I ſuppoſe as above, being more completely fuſed, have become flint coloured by the animal fleſh, but without the exact form either of the fleſh or ſhell of the animal. Many of theſe are hollow within and lined with cryſtals, like the Scot's-pebbles above deſcribed; but as the colouring matter of animal [Page 46] bodies differs but little from each other compared with thoſe of vegetables, theſe flints vary leſs in their colours than thoſe above mentioned. At the ſame time as they cooled in concentric ſpheres like the Scot's-pebbles, they often poſſeſs faint rings of colours, and always break in concholoid forms like them.
This idea of the production of nodules of flint in chalk-beds is countenanced from the iron which generally appears as theſe flints become decompoſed by the air; which by uniting with the iron in their compoſition reduces it from a vitreſcent ſtate to that of calx, and thus renders it viſible. And ſecondly, by there being no appearance in chalk-beds of a ſtring or pipe of ſiliceous matter connecting one nodule with another, which muſt have happened if the ſiliceous matter, or its acid, had been injected from without according to the idea of Dr. Hutton. And thirdly, becauſe many of them have very large cavities at their centres, which ſhould not have happened had they been formed by the injection of a material from without.
When ſhells or chalk are thus converted from calcareous to ſiliceous matter by the fleſh of the animal, the new flint being heavier than the ſhell or chalk occupies leſs ſpace than the materials it was produced from; this is the cauſe of frequent cavities within them, where the whole maſs has not been completely fuſed and preſſed together. In Derbyſhire there are maſſes of coralloid and other ſhells which have become ſiliceous, and are thus left with large vacuities ſometimes within and ſometimes on the outſide of the remaining form of the ſhell, like the French millſtones, and I ſuppoſe might ſerve the ſame purpoſe; the gravel of the Derwent is full of ſpecimens of this kind.
Since writing the above I have received a very ingenious account of chalk-beds from Dr. MENISH of Chelmſford. He diſtinguiſhes chalk-beds into three kinds; ſuch as have been raiſed from the ſea with little diſturbance of their ſtrata, as the cliffs of Dover and Margate, which he terms intire chalk. Another ſtate of chalk is where it has ſuffered much derangement, as the banks of the Thames at Graveſend and Dartford. And a third ſtate where fragments of chalk have been rounded by water, which he terms alluvial chalk. In the firſt of theſe ſituations of chalk he obſerves, that the flint lies in ſtrata horizontally, generally in diſtinct nodules, but that he has obſerved two inſtances of ſolid plates or ſtrata of flint, from an inch to two inches in thickneſs, interpoſed between the chalk-beds; one of theſe is in a chalk-bank by the road ſide at Berkhamſtead, the other in a bank on the road from Chatham leading to Canterbury. Dr. Meniſh has further obſerved, that many of the echini are cruſhed in their form, and yet filled with flint, which has taken the form of the cruſhed ſhell, and that though many flint nodules are hollow, yet that in ſome echini the ſiliceum ſeems to have enlarged, as it paſſed from a fluid to a ſolid ſtate, as it ſwells out in a protuberance at the mouth and anus of the ſhell, and that though theſe ſhells are ſo filled with flint yet that in many places the ſhell itſelf remains calcareous. Theſe ſtrata of nodules and plates of flint ſeem to countenance their origin from the fleſh of a ſtratum of animals which periſhed by ſome natural violence, and were buried in their ſhells.
In many rocks of ſiliceous ſand the particles retain their angular form, and in ſome beds of looſe ſand, of which there is one of conſiderable purity a few yards beneath the marl at Normington about a mile ſouth of Derby. Other ſiliceous ſands have had their angles rounded off, like the pebbles in gravel-beds. Theſe ſeem to owe their globular form to two cauſes; one to their attrition againſt each other, when they may for centuries have lain at the bottom of the ſea, or of rivers; where they may have been progreſſively accumulated, and thus progreſſively at the ſame time rubbed upon each other by the daſhing of the water, and where they would be more eaſily rolled over each other by the their gravity being ſo much leſs than in air. This is evidently now going on in the river Derwent, for though there are no limeſtone rocks for ten or fifteen miles above Derby, yet a great part of the river-gravel at Derby conſiſts of limeſtone nodules, whoſe angles are quite worn off in their deſcent down the ſtream.
There is however another cauſe which muſt have contributed to round the angles both of calcareous and ſiliceous fragments; and that is, their ſolubility in water; calcareous earth is perpetually found ſuſpended in the waters which paſs over it; and the earth of flints was obſerved by Bergman to be contained in water in the proportion of one grain to a gallon. Kirwan's Mineralogy, p. 107. In boiling water, however, it is ſoluble in much greater proportion, as appears from the ſiliceous earth ſublimed in the diſtillation of fluor acid in glaſs veſſels; and from the baſons of calcedony which ſurrounded the jets of hot water near mount Heccla in Iceland. Troil on Iceland. It is probable moſt ſiliceous ſands or pebbles have at ſome ages of the world been long expoſed to aqueous ſteams raiſed by ſubterranean fires. And if fragments of ſtone were long immerſed in a fluid menſtrum, their angular parts would be firſt diſſolved, on account of their greater ſurface.
Many beds of ſiliceous gravel are cemented together by a ſiliceous cement, and are called breccia; as the plumb-pudding ſtones of Hartfordſhire, and the walls of a ſubterraneous temple excavated by Mr. Curzon, at Hagley near Rugely in Staffordſhire; theſe may have been expoſed to great heat as they were immerſed in water; which water under great preſſure of ſuperincumbent materials may have been rendered red-hot, as in Papin's digeſter; and have thus poſſeſſed powers of ſolution with which we are unacquainted.
Another ſourſe of ſiliceous ſtones is from the granite, or baſaltes, or porphyries, which are of different hardneſſes according to the materials of their compoſition, or to the fire they have undergone; ſuch are the ſtones of Arthur's-hill near Edinburgh, of the Giant's Cauſway in Ireland, and of Charnwood Foreſt in Leiceſterſhire; the uppermoſt ſtratum of which laſt ſeems to have been cracked either by its elevation, or by its haſtily cooling after ignition by the contact of dews or ſnows, and thus breaks into angular fragments, ſuch as the ſtreets of London are paved with; or have had their angles rounded by [Page 48] attrition or by partial ſolution; and have thus formed the common paving ſtones or bowlers; as well as the gravel, which is often rolled into ſtrata amid the ſiliceous ſandbeds, which are either formed or collected in the ſea.
In what manner ſuch a maſs of cryſtallized matter as the Giant's Cauſway and ſimilar columns of baſaltes, could have been raiſed without other volcanic appearances, may be a matter not eaſy to comprehend; but there is another power in nature beſides that of expanſile vapour which may have raiſed ſome materials which have previouſly been in igneous or aqueous ſolution; and that is the act of congelation. When the water in the experiments above related of Major Williams had by congelation thrown out the plugs from the bomb-ſhells, a column of ice roſe from the hole of the bomb ſix or eight inches high. Other bodies I ſuſpect increaſe in bulk which cryſtallize in cooling, as iron and type-metal. I remember pouring eight or ten pounds of melted brimſtone into a pot to cool and was ſurprized to ſee after a little time a part of the fluid beneath break a hole in the congealed cruſt above it, and gradually riſe into a promontory ſeveral inches high; the baſaltes has many marks of fuſion and of cryſtallization and may thence, as well as many other kinds of rocks, as of ſpar, marble, petroſilex, jaſper, &c. have been raiſed by the power of congelation, a power whoſe quantity has not yet been aſcertained, and perhaps greater and more univerſal than that of vapours expanded by heat. Theſe baſaltic columns riſe ſometimes out of mountains of granite itſelf, as mentioned by Dr. Beddoes, (Phil. Tranſact. Vol. LXXX.) and as they ſeem to conſiſt of ſimilar materials more completely fuſed, there is ſtill greater reaſon to believe them to have been elevated in the cooling or cryſtallization of the maſs. See note XXIV.
Whence ductile Clays in wide expanſion ſpread,Soft as the Cygnet's down, their ſnow-white bed.CANTO II. l. 276.
THE philoſophers, who have attended to the formation of the earth, have acknowledged two great agents in producing the various changes which the terraqueous globe has undergone, and theſe are water and fire. Some of them have perhaps aſcribed too much to one of theſe great agents of nature, and ſome to the other. They have generally agreed that the ſtratification of materials could only be produced from ſediments or precipitations, which were previouſly mixed or diſſolved in the ſea; and that whatever effects were produced by fire were performed afterwards.
There is however great difficulty in accounting for the univerſal ſtratification of the ſolid globe of the earth in this manner, ſince many of the materials, which appear in ſtrata, could not have been ſuſpended in water; as the nodules of flint in chalk-beds, the extenſive beds of ſhells, and laſtly the ſtrata of coal, clay, ſand, and iron-ore, which in moſt coal-countries lie from five to ſeven times alternately ſtratified over each other, and none of them are ſoluble in water. Add to this if a ſolution of them or a mixture of them in water could be ſuppoſed, the cauſe of that ſolution muſt ceaſe before a precipitation could commence.
1. The great maſſes of lava, under the various names of granite, porphyry, toadſtone, moor-ſtone, rag, and ſlate, which conſtitute the old word, may have acquired the ſtratification, which ſome of them appear to poſſeſs, by their having been formed by ſucceſſive eruptions of a fluid maſs, which at different periods of antient time aroſe from volcanic ſhafts and covered each other, the ſurface of the interior maſs of lava would cool and become ſolid before the ſuperincumbent ſtratum was poured over it; to the ſame cauſe may be aſcribed their different compoſitions and textures, which are ſcarcely the ſame in any two parts of the world.
2. The ſtratifications of the great maſſes of limeſtone, which were produced from ſea-ſhells, ſeem to have been formed by the different times at which the innumerable ſhells were produced and depoſited. A colony of echini, or madrepores, or cornua ammonis, lived and periſhed in one period of time; in another a new colony of either ſimilar or different ſhells lived and died over the former ones, producing a ſtratum of more recent ſhell over a ſtratum of others which had began to petrify or to become marble; and thus from unknown depths to what are now the ſummits of mountains the limeſtone is diſpoſed in ſtrata of varying ſolidity and colour. Theſe have afterwards undergone variety of changes by their ſolution and depoſition from the water in which they were immerſed, or from having been expoſed to great heat under great preſſure, according to the ingenious theory of Dr. Hutton, Edinb. Tranſact. Vol. I. Sec Note XVI.
[Page 50] 3. In moſt of the coal-countries of this iſland there are from five to ſeven beds of coal ſtratified with an equal number of beds, though of much greater thickneſs, of clay and ſandſtone, and occaſionally of iron-ores. In what manner to account for the ſtratification of theſe materials ſeems to be a problem of greater difficulty. Philoſophers have generally ſuppoſed that they have been arranged by the currents of the ſea; but conſidering their inſolubility in water, and their almoſt ſimilar ſpecific gravity, an accumulation of them in ſuch diſtinct beds from this cauſe is altogether inconceiveable, though ſome coal-countries bear marks of having been at ſome time immerſed beneath the waves and raiſed again by ſubterranean fires.
The higher and lower parts of moraſſes were neceſſarily produced at different periods of time, ſee Note XVII. and would thus originally be formed in ſtrata of different ages. For when an old wood periſhed, and produced a moraſs, many centuries would elapſe before another wood could grow and periſh, again upon the ſame ground, which would thus produce a new ſtratum of moraſs over the other, differing indeed principally in its age, and perhaps, as the timber might be different, in the proportions of its component parts.
Now if we ſuppoſe the lowermoſt ſtratum of a moraſs become ignited, like fermenting hay, (after whatever could be carried away by ſolution in water was gone,) what would happen? Certainly the inflammable part, the oil, ſulphur, or bitumen, would burn away, and be evaporated in air; and the fixed parts would be left, as clay, lime, and iron; while ſome of the calcareous earth would join with the ſiliceous acid, and produce ſand, or with the argillaceous earth, and produce marl. Thence after many centuries another bed would take fire, but with leſs degree of ignition, and with a greater body of moraſs over it, what then would happen? The bitumen and ſulphur would riſe and might become condenſed under an impervious ſtratum, which might not be ignited, and there form coal of different purities according to its degree of fluidity, which would permit ſome of the clay to ſubſide through it into the place from which it was ſublimed.
Some centuries afterwards another ſimilar proceſs might take place, and either thicken the coal-bed, or produce a new clay-bed, or marl, or ſand, or depoſit iron upon it, according to the concomitant circumſtances above mentioned.
I do not mean to contend that a few maſſes of ſome materials may not have been rolled together by currents, when the mountains were much more elevated than at preſent, and in conſequence the rivers broader and more rapid, and the ſtorms of rain and wind greater both in quantity and force. Some gravel-beds may have been thus waſhed from the mountains; and ſome white clay waſhed from moraſſes into valleys beneath them; and ſome ochres of iron diſſolved and again depoſited by water; and ſome calcareous depoſitions from water, (as the bank for inſtance on which ſtand the houſes at Matlock-bath;) but theſe are of ſmall extent or conſequence compared to the primitive rocks of granite or porpyhry which form the nucleus of the earth, or to the immenſe ſtrata of limeſtone which cruſt over the greateſt part of this granite or porphyry; or laſtly to the very extenſive beds of clay, marl, ſandſtone, coal, and iron, [Page 51] which were probably for many millions of years the only parts of our continents and iſlands, which were then elevated above the level of the ſea, and which on that account became covered with vegetation, and thence acquired their later or ſuperincumbent ſtrata, which conſtitute, what ſome have termed, the new world.
There is another ſource of clay, and that of the fineſt kind, from decompoſed granite, this is of a ſnowy white and mixed with ſhining particles of mica, of this kind is an earth from the country of Cherokees. Other kinds are from leſs pure lavas; Mr. Ferber aſſerts that the ſulphurous ſteams from Mount Veſuvius convert the lava into clay.
‘The lavas of the antient Solfatara volcano have been undoubtedly of a vitreous nature, and theſe appear at preſent argillaceous. Some fragments of this lava are but half or at one ſide changed into clay, which either is viſcid or ductile, or hard and ſtoney. Clays by fire are deprived of their coherent quality, which cannot be reſtored to them by pulverization, nor by humectation. But the ſulphureous Solfatara ſteams reſtore it, as may be eaſily obſerved on the broken pots wherein they gather the ſal ammoniac; though very well baked and burnt at Naples they are mollified again by the acid ſteams into a viſcid clay which keeps the ſormer fire-burnt colour. Travels in Italy, p. 156. ’
Smear'd her huge dragons with metallic hues,With golden purples, and cobaltic blues;CANTO II l. 287.
In Europe the application of gold to theſe purpoſes appears to be of modern invention. Caſſius's diſcovery of the precipitate of gold by tin, and the uſe of that precipitate for colouring glaſs and enamels, are now generally known, but though the precipitate with tin be more ſucceſſful in producing the ruby glaſs, or the colourleſs glaſs which becomes red by ſubſequent ignition, the tin probably contributing to prevent the gold from ſeparating, (which it is very liable to do during the fuſion; yet, for enamels, the precipitates made by alcaline ſalts anſwer equally well, and give a finer red, the colour produced by the tin precipitate being a bluiſh purple, but with the others a roſe red. I am informed that ſome of our beſt artiſts prefer aurum fulminans, mixing it, before it has become dry, with the white compoſition or enamel flux; when once it is divided by the other matter, it is ground with great ſafety, and without the leaſt danger of exploſion, whether moiſt or dry. The colour is remarkably improved and brought forth by long grinding, which accordingly makes an eſſential circumſtance in the proceſs.
[Page 52] The precipitates of gold, and the colcothar or other red preparations of iron, are called tender colours. The heat muſt be no greater than is juſt ſufficient to make the enamel run upon the piece, for if greater, the colours will be deſtroyed or changed to a different kind. When the vitreous matter has juſt become fluid it ſeems as if the coloured metallic calx remained barely intermixed with it, like a coloured powder of exquiſite tenuity ſuſpended in water: but by ſtronger fire the calx is diſſolved, and metallic colours are altered by ſolution in glaſs as well as in acids or alcalies.
The Saxon mines have till very lately almoſt excluſively ſupplied the reſt of Europe with cobalt, or rather with its preparations, zaffre and ſmalt, for the exportation of the ore itſelf is there a capital crime. Hungary, Spain, Sweden, and ſome other parts of the continent, are now ſaid to afford cobalts equal to the Saxon, and ſpecimens have been diſcovered in our own iſland, both in Cornwall and in Scotland; but hitherto in no great quantity.
Calces of cobalt and of copper differ very materially from thoſe above mentioned in their application for colouring enamels. In thoſe the calx has previouſly acquired the intended colour, a colour which bears a red heat without injury, and all that remains is to fix it on the piece by a vitreous flux. But the blue colour of cobalt, and the green or bluiſh green of copper, are produced by vitrification, that is, by ſolution in the glaſs, and a ſtrong fire is neceſſary for their perfection. Theſe calces therefore, when mixed with the enamel flux, are melted in crucibles, once or oftener, and the deep coloured opake glaſs, thence reſulting, is ground into unpalpable powder, and uſed for enamel. One part of either of theſe calces is put to ten, ſixteen, or twenty parts of the flux, according to the depth of colour required. The heat of the enamel kiln is only a full red, ſuch as is marked on Mr. Wedgwood's thermometer 6 degrees. It is therefore neceſſary that the flux be ſo adjuſted as to melt in that low heat. The uſual materials are flint, or flint-glaſs, with a due proportion of red-led, or borax, or both, and ſometimes a little tin calx to give opacity.
Or bid Mortality rejoice or mournO'er the fine forms of Portland's myſtic urn.CANTO II. l 321.
THE celebrated funereal vaſe, long in poſſeſſion of the Barberini family, and lately purchaſed by the Duke of Portland for a thouſand guineas, is about ten inches high and ſix in diameter in the broadeſt part. The figures are of moſt exquiſite workmanſhip in bas relief of white opake glaſs, raiſed on a ground of deep blue glaſs, which appears black except when held againſt the light. Mr. Wedgwood is of opinion from many circumſtances that the figures have been made by cutting away the external cruſt of white opake glaſs, in the manner the fineſt cameo's have been produced, and that it muſt thence have been the labour of a great many years. Some antiquarians have placed the time of its production many centuries before the chriſtian aera; as ſculpture was ſaid to have been declining in reſpect to its excellence in the time of Alexander the Great. See an account of the Barberini or Portland vaſe by M. D'Hancarville, and by Mr. Wedgwood.
Many opinions and conjectures have been publiſhed concerning the figures on this celebrated vaſe. Having carefully examined one of Mr. Wedgwood's beautiful copies of this wonderful production of art, I ſhall add one more conjecture to the number.
Mr. Wedgwood has well obſerved that it does not ſeem probable that the Portland vaſe was purpoſely made for the aſhes of any particular perſon deceaſed, becauſe many years muſt have been neceſſary for its production. Hence it may be concluded, that the ſubject of its embelliſhments is not private hiſtory but of a general nature. This ſubject appears to me to be well choſen, and the ſtory to be finely told; and that it repreſents what in antient times engaged the attention of philoſophers, poets, and heroes, I mean a part of the Eleuſinian myſteries.
Theſe myſteries were invented in Aegypt, and afterwards tranſferred to Greece, and flouriſhed more particularly at Athens, which was at the ſame time the ſeat of the fine arts. They conſiſted of ſcenical exhibitions repreſenting and inculcating the expectation of a future life after death, and on this account were encouraged by the government, inſomuch that the Athenian laws puniſhed a diſcovery of their ſecrets with death. Dr. Warburton has with great learning and ingenuity ſhewn that the deſcent of Aeneas into hell, deſcribed in the Sixth Book of Virgil, is a poetical account of the repreſentations of the future ſtate in the Eleuſinian myſteries. Divine Legation, Vol. I. p, 210.
And though ſome writers have differed in opinion from Dr. Warburton on this ſubject, becauſe Virgil has introduced ſome of his own heroes into the Elyſian fields, as Deiphobus, Palinurus, and Dido, in the ſame manner as Homer had done before him, yet it is agreed that the received notions about a future ſtate were exhibited in theſe myſteries, and as theſe poets deſcribed thoſe received notions, they may be ſaid, as far as theſe religious doctrines were concerned, to have deſcribed the myſteries.
[Page 54] Now as theſe were emblematic exhibitions they muſt have been as well adapted to the purpoſes of ſculpture as of poetry, which indeed does not ſeem to have been uncommon, ſince one compartment of figures in the ſheild of Aeneas repreſented the regions of Tartarus. Aen. Lib. X. The proceſſion of torches, which according to M. De St. Croix was exhibited in theſe myſteries, is ſtill to be ſeen in baſſo relievo, diſcovered by Spon and Wheler. Memoires ſur le Myſteres par De St. Croix. 1784. And it is very probable that the beautiful gem repreſenting the marriage of Cupid and Pſyche, as deſcribed by Apulcus, was originally deſcriptive of another part of the exhibitions in theſe myſteries, though afterwards it became a common ſubject of antient art. See Divine Legat. Vol. I. p. 323. What ſubject could have been imagined ſo ſublime for the ornaments of a funereal urn as the mortality of all things and their reſuſcitation? Where could the deſigner be ſupplied with emblems for this purpoſe, before the Chriſtian aera, but from the Eleuſinian myſteries?
1. The exhibitions of the myſteries were of two kinds, thoſe which the people were permitted to ſee, and thoſe which were only ſhewn to the initiated. Concerning the latter, Ariſtides calls them ‘the moſt ſhocking and moſt raviſhing repreſentations.’ And Stoboeus aſſerts that the initiation into the grand myſteries exactly reſembles death. Divine Legat. Vol. I. p. 280, and p. 272. And Virgil in his entrance to the ſhades below, amongſt other things of terrible form, mentions death. Aen. VI. This part of the exhibition ſeems to be repreſented in one of the compartments of the Portland vaſe.
Three figures of exquiſite workmanſhip are placed by the ſide of a ruined column whoſe capital is fallen off, and lies at their feet with other diſjointed ſtones, they ſit on looſe piles of ſtone beneath a tree, which has not the leaves of any evergreen of this climate, but may be ſuppoſed to be an elm, which Virgil places near the entrance of the infernal regions, and adds, that a dream was believed to dwell under every leaf of it. Aen. VI. l. 281. In the midſt of this group reclines a female figure in a dying attitude, in which extreme languor is beautifully repreſented, in her hand is an inverted torch, an antient emblem of extinguiſhed life, the elbow of the ſame arm reſting on a ſtone ſupports her as ſhe ſinks, while the other hand is raiſed and thrown over her drooping head, in ſome meaſure ſuſtaining it and gives with great art the idea of fainting laſſitude. On the right of her ſits a man, and on the left a woman, both ſupporting themſelves on their arms, as people are liable to do when they are thinking intenſely. They have their backs towards the dying figure, yet with their faces turned towards her, as if ſeriouſly contemplating her ſituation, but without ſtretching out their hands to aſſiſt her.
The man and woman on each ſide of the dying figure muſt be conſidered as emblems, both from their ſimilarity of ſituation and dreſs to the middle figure, and their being grouped along with it. Theſe I think are hieroglyphic or Eleuſinian emblems of HUMANKIND, with their backs toward the dying figure of MORTAL LIFE, unwilling to aſſociate with her, yet turning back their ſerious and attentive countenances, curious indeed to behold, yet ſorry to contemplate their latter end. Theſe figures bring ſtrongly to one's mind the Adam and Eve of ſacred writ, whom ſome have ſuppoſed to have been allegorical or hieroglyphic perſons of Aegyptian origin, but of more antient date, amongſt whom I think is Dr. Warburton. According to this opinion Adam and Eve were the names of two hieroglyphic figures repreſenting the early ſtate of mankind; Abel was the name of an hieroglyphic figure repreſenting the age of paſturage, and Cain the name of another hieroglyphic ſymbol repreſenting the age of agriculture, at which time the uſes of iron were diſcovered. And as the people who cultivated the earth and built houſes would increaſe in numbers much faſter by their greater production of food, they would readily conquer or deſtroy the people who were ſuſtained by paſturage, which was typified by Cain ſlaying Abel.
2. On the other compartment of this celebrated vaſe is exhibited an emblem of immortality, the repreſentation of which was well known to conſtitute a very principal part of the ſhews at the Eleuſinian myſteries, as Dr. Warburton has proved by variety of authority. The habitation of ſpirits or ghoſts after death was ſuppoſed by the antients to be placed beneath the earth, where Pluto reigned, and diſpenſed rewards or puniſhments. Hence the firſt figure in this group is of the MANES or GHOST, who having paſſed through an open portal is deſcending into a duſky region, pointing his toe with timid and unſteady ſtep, feeling as it were his way in the gloom. This portal Aeneas enters, which is deſcribed by Virgil,—patet atri janua ditis, Aen. VI. l. 126; as well as the eaſy deſcent,—facilis deſcenſus Averni. Ib. The darkneſs at the entrance to the ſhades is humorouſly deſcribed by Lucian. Div. Legat. Vol. I. p. 241. And the horror of the gates of hell was in the time of Homer become a proverb; Achilles ſays to Ulyſſes, "I hate a liar worſe than the gates of hell;" the ſame expreſſion is uſed in Iſaiah, ch. xxxviii. v. 10. The MANES or GHOST appears lingering and fearful, and wiſhes to drag after him a part of his mortal garment, which however adheres to the ſide of the portal through which he has paſſed. The beauty of this allegory would have been expreſſed by Mr. Pope, by "We feel the ruling paſſion ſtrong in death."
A little lower down in the group the manes or ghoſt is received by a beautiful female, a ſymbol of IMMORTAL LIFE. This is evinced by her fondling between her knees a large and playful ſerpent, which from its annually renewing its external ſkin has from great antiquity, even as early as the fable of Prometheus, been eſteemed an emblem of [Page 56] renovated youth. The ſtory of the ſerpent acquiring immortal life from the aſs of Prometheus, who carried it on his back, is told in Bacon's Works, Vol. V. p. 462. Quarto edit. Lond. 1778. For a ſimilar purpoſe a ſerpent was wrapped round the large hieroglyphic egg in the temple of Dioſcuri, as an emblem of the renewal of life from a ſtate of death. Bryant's Mythology, Vol II. p. 359. ſec. edit. On this account alſo the ſerpent was an attendant on Aeſculapius, which ſeems to have been the name of the hieroglyphic figure of medicine. This ſerpent ſhews this figure to be an emblem, as the torch ſhewed the central figure of the other compartment to be an emblem, hence they agreeably correſpond, and explain each other, one repreſenting MORTAL LIFE, and the other IMMORTAL LIFE.
This emblematic figure of immortal life ſits down with her feet towards the figure of Pluto, but, turning back her face towards the timid ghoſt, ſhe ſtretches forth her hand, and taking hold of his elbow, ſupports his tottering ſteps, as well as encourages him to advance, both which circumſtances are thus with wonderful ingenuity brought to the eye. At the ſame time the ſpirit looſely lays his hand upon her arm, as one walking in the dark would naturally do for the greater certainty of following his conductreſs, while the general part of the ſymbol of IMMORTAL LIFE, being turned toward the figure of Pluto, ſhews that ſhe is leading the phantom to his realms.
In the Pamphili gardens at Rome, Perſeus in aſſiſting Andromeda to deſcend from the rock takes hold of her elbow to ſteady or ſupport her ſtep, and ſhe lays her hand looſely on his arm as in this figure. Admir. Roman. Antiq.
The figure of PLUTO can not be miſtaken, as is agreed by moſt of the writers who have mentioned this vaſe; his griſley beard, and his having one foot buried in the earth, denotes the infernal monarch. He is placed at the loweſt part of the group, and reſting his chin on his hand, and his arm upon his knee, receives the ſtranger-ſpirit with inquiſitive attention; it was before obſerved that when people think attentively they naturally reſt their bodies in ſome eaſy attitude, that more animal power may be employed on the thinking faculty. In this group of figures there is great art ſhewn in giving an idea of a deſcending plain, viz. from earth to Elyſium, and yet all the figures are in reality on an horizontal one. This wonderful deception is produced firſt by the deſcending ſtep of the manes or ghoſt; ſecondly, by the arm of the ſitting figure of immortal life being raiſed up to receive him as he deſcends; and laſtly, by Pluto having one foot ſunk into the earth.
There is yet another figure which is concerned in conducting the manes or ghoſt to the realms of Pluto, and this is LOVE. He precedes the deſcending ſpirit on expanded wings, lights him with his torch, and turning back his beautiful countenance beckons him to advance. The antient God of love was of much higher dignity than the modern Cupid. He was the firſt that came out of the great egg of night, (Heſiod. Theog. V. CXX. Bryant's Mythol. Vol. II. p. 348.) and is ſaid to poſſeſs the keys of the ſky, ſea, and earth. As he therefore led the way into this life, he ſeems to conſtitute a proper emblem for leading the way to a ſuture life. See Bacon's works. Vol. I. p. 568. and Vol. III. p. 582. Quarto edit.
[Page 57] The introduction of love into this part of the myſteries requires a little further explanation. The Pſyche of the Aegyptians was one of their moſt favourite emblems, and repreſented the ſoul, or a future life; it was originally no other than the aurelia, or butterfly, but in after times was repreſented by a lovely female child with the beautiful wings of that inſect. The aurelia, after its firſt ſtage as an eruca or caterpillar, lies for a ſeaſon in a manner dead, and is incloſed in a ſort of coffin, in this ſtate of darkneſs it remains all the winter, but at the return of ſpring it burſts its bonds and comes out with new life, and in the moſt beautiful attire. The Aegyptians thought this a very proper picture of the ſoul of man, and of the immortality to which it aſpired. But as this was all owing to divine Love, of which EROS was an emblem, we find this perſon frequently introduced as a concomitant of the ſoul in general or Pſyche. (Bryant's Mythol. Vol. II. p. 386.) EROS, or divine Love, is for the ſame reaſon a proper attendant on the manes or ſoul after death, and much contributes to tell the ſtory, that is, to ſhew that a ſoul or manes is deſigned by the deſcending figure. From this figure of Love M. D'Hancarville imagines that Orpheus and Eurydice are typified under the figure of the manes and immortal life as above deſcribed. It may be ſufficient to anſwer, firſt, that Orpheus is always repreſented with a lyre, of which there are prints of four different gems in Spence's Polymetis, and Virgil ſo deſcribes him, Aen. VI. cytharâ. fretus. And ſecondly, that it is abſurd to ſuppoſe that Eurydice was fondling and playing with a ſerpent that had ſlain her. Add to this that Love ſeems to have been an inhabitant of the infernal regions, as exhibited in the myſteries, for Claudian, who treats more openly of the Eleuſinian myſteries, when they were held in leſs veneration, invokes the deities to diſcloſe to him their ſecrets, and amongſt other things by what torch Love ſoftens Pluto.
Dii, quibus in numerum, &c.Vos mihi ſacrarum penetralia pandite rerum,Et veſtri ſecreta poli, quâ lampade DitemFlexit amor.
In this compartment there are two trees, whoſe branches ſpread over the figures, one of them has ſmoother leaves like ſome evergreens, and might thence be ſuppoſed to have ſome alluſion to immortality, but they may perhaps have been deſigned only as ornaments, or to relieve the figures, or becauſe it was in groves, where theſe myſteries were originally celebrated. Thus Homer ſpeaks of the woods of Proſerpine, and mentions many trees in Tartarus, as preſenting their fruits to Tantalus; Virgil ſpeaks of the pleaſant groves of Elyſium; and in Spence's Polymetis there are prints of two antient gems, one of Orpheus charming Cerberus with his lyre, and the other of Hercules binding him in a cord, each of them ſtanding by a tree. Polymet. p. 284. As however theſe trees have all different foliage ſo clearly marked by the artiſt, they may have had ſpecific meanings in the exhibitions of the myſteries, which have not reached poſterity, of this kind ſeem to have been the tree of knowledge of good and evil, and the tree of life, in ſacred writ, both which muſt have been emblematic or allegorical. The maſks, [Page 58] hanging to the handles of the vaſe, ſeem to indicate that there is a concealed meaning in the figures beſides their general appearance. And the prieſteſs at the bottom, which I come now to deſcribe, ſeems to ſhew this concealed meaning to be of the ſacred or Eleuſinian kind.
3. The figure on the bottom of the vaſe is on a larger ſcale than the others, and leſs finely finiſhed, and leſs elevated, and as this bottom part was afterwards cemented to the upper part, it might be executed by another artiſt for the ſake of expedition, but there ſeems no reaſon to ſuppoſe that it was not originally deſigned for the upper part of it as ſome have conjectured. As the myſteries of Ceres were celebrated by female prieſts, for Porphyrius ſays the antients called the prieſteſſes of Ceres, Meliſſai, or bees, which were emblems of chaſtity. Div. Leg. Vol. I. p. 235. And as, in his Satire againſt the ſex, Juvenal ſays, that few women are worthy to be prieſteſſes of Ceres. Sat. VI. the figure at the bottom of the vaſe would ſeem to repreſent a PRIESTESS or HIEROPHANT, whoſe office it was to introduce the initiated, and point out to them, and explain the exhibitions in the myſteries, and to exclude the uninitiated, calling out to them, " Far, far retire, ye profane!" and to guard the ſecrets of the temple. Thus the introductory hymn ſung by the hierophant, according to Euſebius, begins, "I will declare a ſecret to the initiated, but let the doors be ſhut againſt the profane." Div. Leg. Vol. I. p. 177. The prieſteſs or hierophant appears in this figure with a cloſe hood, and dreſſed in linen, which ſits cloſe about her; except a light cloak, which flutters in the wind. Wool, as taken from ſlaughtered animals, was eſteemed profane by the prieſts of Aegypt, who were always dreſſed in linen. Apuleus, p. 64. Div. Leg. Vol. I. p. 318. Thus Eli made for Samuel a linen ephod. Samuel i. 3.
Secrecy was the foundation on which all myſteries reſted, when publicly known they ceaſed to be myſteries; hence a diſcovery of them was not only puniſhed with death by the Athenian law; but in other countries a diſgrace attended the breach of a ſolemn oath. The prieſteſs in the figure before us has her finger pointing to her lips as an emblem of ſilence. There is a figure of Harpocrates, who was of Aegyptian origin, the ſame as Orus, with the lotus on his head, and with his finger pointing to his lips not preſſed upon them, in Bryant's Mythol. Vol. II. p. 398, and another female figure ſtanding on a lotus, as if juſt riſen from the Nile, with her finger in the ſame attitude, theſe ſeem to have been repreſentations or emblems of male and female prieſts of the ſecret myſteries. As theſe ſort of emblems were frequently changed by artiſts for their more elegant exhibition, it is poſſible the foliage over the head of this figure may bear ſome analogy to the lotus above mentioned.
This figure of ſecrecy ſeems to be here placed, with great ingenuity, as a caution to the initiated, who might underſtand the meaning of the emblems round the vaſe, not to divulge it. And this circumſtance ſeems to account for there being no written explanation extant, and no tradition concerning theſe beautiful figures handed down to us along with them.
In the Muſeum Etruſcum, Vol. I. plate 96, there is the head of Atis with feminine features, clothed with a Phrygian cap, and riſing from very broad foliage, placed on a kind of term ſupported by the paw of a lion. Goreus in his explanation of the figure ſays that it is placed on a lion's foot becauſe that animal was ſacred to Cybele, and that it riſes from very broad leaves becauſe after he became an eunuch he determined to dwell in the groves. Thus the foliage, as well as the cap and feminine features, confirm the idea of this figure at the bottom of the vaſe repreſenting the head of Atis the firſt great hierophant, and that the figures on the ſides of the vaſe are emblems from the antient myſteries.
I beg leave to add that it does not appear to have been uncommon amongſt the antients to put allegorical figures on funeral vaſes. In the Pamphili palace at Rome there is an elaborate repreſentation of Life and of Death, on an antient ſarcophagus. In the firſt Prometheus is repreſented making man, and Minerva is placing a butterfly, or the foul, upon his head. In the other compartment Love extinguiſhes his torch in the boſom of the dying figure, and is receiving the butterfly, or Pſyche, from him, with a great number of complicated emblematic figures grouped in very bad taſte. Admir. Roman. Antiq.
Whence ſable Coal his maſſy couch extends,And ſtars of gold the ſparkling Pyrite blends.CANTO II. l. 349.
TO elucidate the formation of coal-beds I ſhall here deſcribe a fountain of foſſil tar, or petroleum, diſcovered lately near Colebrook Dale in Shropſhire, the particulars of which were ſent me by Dr. Robert Darwin of Shrewſbury.
About a mile and a half below the celebrated iron-bridge, conſtructed by the late Mr. DARBY near Colebrook Dale, on the eaſt ſide of the river Severn, as the workmen in October 1786 were making a ſubterranean canal into the mountain, for the more eaſy acquiſition and conveyance of the coals which lie under it, they found an oozing of liquid bitumen, or petroleum; and as they proceeded further cut through ſmall cavities of different ſizes from which the bitumen iſſued. From ten to fifteen barrels of this foſſil tar, each barrel containing thirty-two gallons, were at firſt collected in a day, which has ſince however gradually diminiſhed in quantity, ſo that at preſent the product is about ſeven barrels in fourteen days.
The mountain, into which this canal enters, conſiſts of ſiliceous ſand, in which however a few marine productions, apparently in their recent ſtate, have been found, and are now in the poſſeſſion of Mr. WILLIAM REYNOLDS of Ketly Bank. About three hundred yards from the entrance into the mountain, and about twenty-eight yards below the ſurface of it, the tar is found oozing from the ſand-rock above into the top and ſides of the canal.
Beneath the level of this canal a ſhaft has been ſunk through a grey argillaceous ſubſtance, called in this country clunch, which is ſaid to be a pretty certain indication of coal; beneath this lies a ſtratum of coal, about two or three inches thick, of an inferior kind, yielding little flame in burning, and leaving much aſhes; below this is a rock of a harder texture; and beneath this are found coals of an excellent quality; for the purpoſe of procuring which with greater facility the canal, or horizontal aperture, is now making into the mountain. July, 1788.
Beneath theſe coals in ſome places is found ſalt water, in other parts of the adjacent country there are beds of iron-ſtone, which alſo contain ſome bitumen in a leſs fluid ſtate, and which are about on a level with the new canal, into which the foſſil tar oozes, as above deſcribed.
There are many intereſting circumſtances attending the ſituation and accompaniments of this fountain of foſſil tar, tending to develop the manner of its production. 1. As the canal paſſing into the mountain runs over the beds of coals, and under the reſervoir of petroleum, it appears that a natural diſtillation of this foſſil in the bowels of the earth muſt have taken place at ſome early period of the world, ſimilar to the artificial diſtillation [Page 61] of coal, which has many years been carried on in this place on a ſmaller ſcale above ground. When this reſervoir of petroleum was cut into, the ſlowneſs of its exſudation into the canal was not only owing to its viſcidity, but to the preſſure of the atmoſphere, or to the neceſſity there was that air ſhould at the ſame time inſinuate itſelf into the ſmall cavities from which the petroleum deſcended. The exiſtence of ſuch a diſtillation at ſome antient time is confirmed by the thin ſtratum of coal beneath the canal, (which covers the hard rock,) having been deprived of its foſſil oil, ſo as to burn without flame, and thus to have become a natural coak, or foſſil charcoal, while the petroleum diſtilled from it is found in the cavities of the rock above it.
There are appearances in other places, which favour this idea of the natural diſtillation of petroleum, thus at Matlock in Derbyſhire a hard bitumen is found adhering to the ſpar in the clefts of the lime-rocks in the form of round drops about the ſize of peas; which could perhaps only be depoſited there in that form by ſublimation.
2. The ſecond deduction, which offers itſelf, is, that theſe beds of coal have been expoſed to a conſiderable degree of heat, ſince the petroleum above could not be ſeparated, as far as we know, by any other means, and that the good quality of the coals beneath the hard rock was owing to the impermeability of this rock to the bituminous vapour, and to its preſſure being too great to permit its being removed by the elaſticity of that vapour. Thus from the degree of heat, the degree of preſſure, and the permeability of the ſuperincumbent ſtrata, many of the phenomena attending coal-beds receive an eaſy explanation, which much accords with the ingenious theory of the earth by Dr. Hutton. Trans. of Edinb. Vol. I.
In ſome coal works the fuſion of the ſtrata of coal has been ſo ſlight, that there remains the appearance of ligneus fibres, and the impreſſion of leaves, as at Bovey near Exeter, and even ſeeds of vegetables, of which I have had ſpecimens from the collieries near Poleſworth in Warwickſhire. In ſome, where the heat was not very intenſe and the incumbent ſtratum not permeable to vapour, the foſſil oil has only riſen to the upper part of the coal-bed, and has rendered that much more inflammable than the lower parts of it, as in the collieries near Beaudeſert, the ſeat of the EARL OF UXBRIDGE in Staffordſhire, where the upper ſtratum is a perfect cannel, or candle-coal, and the lower one of an inferior quality. Over the coal-beds near Sir H. HARPUR's houſe in Derbyſhire a thin lamina of aſphaltum is found in ſome places near the ſurface of the earth, which would ſeem to be from a diſtillation of petroleum from the coals below, the more fluid part of which had in proceſs of time exhaled, or been conſolidated by its abſorption of air. In other coal-works the upper part of the ſtratum is of a worſe kind than the lower one, as at Alfreton and Denbigh in Derbyſhire, owing to the ſupercumbent ſtratum having permitted the exhalation of a great part of the petroleum; whilſt at Widdrington in Northumberland there is firſt a ſeam of coal about ſix inches thick of no value, which lies under about four fathom of clay, beneath this is a white freeſtone, then a hard ſtone, which the workmen there call a whin, then two fathoms of clay, then another white ſtone, and under that a vein of coals three feet nine inches [Page 62] thick, of a ſimilar nature to the Newcaſtle coal. Phil. Trans. Abridg. Vol. VI. plate II. p. 192. The ſimilitude between the circumſtances of this colliery, and of the coal beneath the fountain of tar above deſcribed, renders it highly probable that this upper thin ſeam of coal has ſuffered a ſimilar diſtillation, and that the inflammable part of it had either been received into the clay above in the form of ſulphur, which when burnt in the open air would produce alum; or had been diſſipated for want of a receiver, where it could be condenſed. The former opinion is perhaps in this cafe more probable as in ſome other coal-beds, of which I have procured accounts, the ſurface of the coal beneath clunch or clay is of an inferior quality, as at Weſt Hallum in Nottinghamſhire. The clunch probably from hence acquires its inflammable part, which on calcination becomes vitriolic acid. I gathered pieces of clunch converted partially into alum at a colliery near Bilſton, where the ground was ſtill on fire a few years ago.
The heat, which has thus pervaded the beds of moraſs, ſeems to have been the effect of the fermentation of their vegetable materials; as new hay ſometimes takes fire even in ſuch very ſmall maſſes from the ſugar it contains, and ſeems hence not to have been attended with any expulſion of lava, like the deeper craters of volcanos ſituated in beds of granite.
3. The marine ſhells found in the looſe ſand-rock above this reſervoir of petroleum, and the coal-beds beneath it, together with the exiſtence of ſea-ſalt beneath theſe coals, prove that theſe coal beds have been at the bottom of the ſea, during ſome remote period of time, and were afterwards raiſed into their preſent ſituation by ſubterraneous expanſions of vapour. This doctrine is further ſupported by the marks of violence, which ſome coal-beds received at the time they were raiſed out of the ſea, as in the collieries at Mendip in Somerſetſhire. In theſe there are ſeven ſtrata of coals, equitant upon each other, with beds of clay and ſtone intervening; amongſt which clay are found ſhells and fern branches. In one part of this hill the ſtrata are diſjoined, and a quantity of heterogeneous ſubſtances fill up the chaſm which diſjoins them, on one ſide of this chaſm the ſeven ſtrata of coal are ſeen correſponding in reſpect to their reciprocal thickneſs and goodneſs with the ſeven ſtrata on the other ſide of the cavity, except that they have been elevated ſeveral yards higher. Phil. Tranſ. No. 360. abridg. Vol. V. p. 237.
The cracks in the coal-bed near Ticknall in Derbyſhire, and in the ſand-ſtone rock over it, in both of which ſpecimens of lead-ore and ſpar are found, confirm this opinion of their having been forcibly raiſed up by ſubterraneous fires. Over the colliery at Brown-hills near Lichfield, there is a ſtratum of gravel on the ſurface of the ground; which may be adduced as another proof to ſhew that thoſe coals had ſome time been beneath the ſea, or the bed of a river. Nevertheleſs, theſe arguments only apply to the collieries above mentioned, which are few compared with thoſe which bear no marks of having been immerſed in the ſea.
On the other hand the production of coals from moraſſes, as deſcribed in note XX. is evinced from the vegetable matters frequently found in them, and in the ſtrata over them; as fern-leaves in nodules of iron-ore, and from the bog-ſhells or freſh water [Page 63] muſcles ſometimes found over them, of both which I have what I believe to be ſpecimens; and is further proved from ſome parts of theſe beds being only in part transformed to coal; and the other part ſtill retaining not only the form, but ſome of the properties of wood; ſpecimens of which are not unfrequent in the cabinets of the curious, procured from Loch Neigh in Ireland, from Bovey near Exeter, and other places; and from a famous cavern called the Temple of the Devil, near the town of Altorf in Franconia, at the foot of a mountain covered with pine and ſavine, in which are found large coals reſembling trees of ebony; which are ſo far mineralized as to be heavy and compact; and ſo to effloreſce with pyrites in ſome parts as to crumble to pieces; yet from other parts white aſhes are produced on calcination, from which fixed alcali is procured; which evinces their vegetable origin. (Dict. Raiſonné, art. Charbon.) To theſe may be added another argument from the oil which is diſtilled from coals, and which is analogous to vegetable oil, and does not exiſt in any bodies truly mineral. Keir's Chemical Dictionary, art. Bitumen.
Whence it would appear, that though moſt collieries with their attendant ſtrata of clay, ſand-ſtone, and iron, were formed on the places where the vegetables grew, from which they had their origin; yet that other collections of vegetable matter were waſhed down from eminences by currents of waters into the beds of rivers, or the neighbouring ſeas, and were there accumulated at different periods of time, and underwent a great degree of heat from their fermentation, in the ſame manner as thoſe beds of moraſs which had continued on the plains where they were produced. And that by this fermentation many of them had been raiſed from the ocean with ſand and ſea-ſhells over them; and others from the beds of rivers with accumulations of gravel upon them.
4. For the purpoſe of bringing this hiſtory of the products of moraſſes more diſtinctly to the eye of the reader, I ſhall here ſubjoin two or three accounts of ſinking or boring for coals, out of above twenty which I have procured from various places, though the terms are not very intelligible, being the language of the overſeers of coal-works.
1. Whitfield mine near the Pottery in Staffordſhire. Soil 1 foot. brick-clay 3 feet. ſhale 4. metal which is hard brown and falls in the weather 42. coal 3. warrant clay 6. brown gritſtone 36. coal 3 ½. warrant clay 3 ½. baſs and metal 53 ½. hardſtone 4. ſhaly baſs 1 ½. coal 4. warrant clay, depth unknown. in all about 55 yards.
2. Coal-mine at Alfreton in Derbyſhire. Soil and clay 7 feet. fragments of ſtone 9. bind 13. ſtone 6. bind 34. ſtone 5. bind 2. ſtone 2. bind 10. coal 1 ½. bind 1 ½. ſtone 37. bind 7. ſoft coal 3. bind 3. ſtone 20. bind 16. coal 7 ½. in all about 61 yards.
3. A baſſet coal-mine at Woolartan in Nottinghamſhire. Sand and gravel 6 feet. bind 21. ſtone 10. ſmut or effete coal 1. clunch 4. bind 21. ſtone 18. bind 18. ſtonebind 15. ſoft coal 2. clunch and bind 21. coal 7. in all about 48 yards.
4. Coal-mine at Weſt-Hallam in Nottinghamſhire. Soil and clay 7 feet. bind 48. ſmut 1 ½. clunch 4. bind 3. ſtone 2. bind 1. ſtone 1. bind 3. ſtone 1. bind 16. ſhale 2. bind 12. ſhale 3. clunch, ſtone, and a bed of cank 54. ſoft coal 4. clay and dun 1. ſoft coal 4 ½. clunch and bind 21. coal 1. broad bind 26. hard coal 6. in all about 74 yards.
[Page 64] As theſe ſtrata generally lie inclined, I ſuppoſe parallel with the limeſtone on which they reſt, the upper edges of them all come out to day, which is termed baſſetting; when the whole maſs was ignited by its fermentation, it is probable that the inflammable part of ſome ſtrata might thus more eaſily eſcape than of others in the form of vapour; as dews are known to ſlide between ſuch ſtrata in the production of ſprings; which accounts for ſome coal-beds being ſo much worſe than others. See note XX.
Climb the rude ſteeps, the Granite-cliffs ſurround.CANTO II. l. 522.
THE loweſt ſtratum of the earth which human labour has arrived to, is granite; and of this likewiſe conſiſts the higheſt mountains of the world. It is known under variety of names according to ſome difference in its appearance or compoſition, but is now generally conſidered by philoſophers as a ſpecies of lava; if it contains quartz, feltſpat, and mica in diſtinct cryſtals, it is called granite; which is found in Cornwall in rocks; and in looſe ſtones in the gravel near Drayton in Shropſhire, in the road towards Newcaſtle. If theſe parts of the compoſition be leſs diſtinct, or if only two of them be viſible to the eye, it is termed porphyry, trap, whinſtone, moorſtone, ſlate. And if it appears in a regular angular form, it is called baſaltes. The affinity of theſe bodies has lately been further well eſtabliſhed by Dr. Beddoes in the Phil. Tranſ. Vol. LXXX.
Theſe are all eſteemed to have been volcanic productions that have undergone different degrees of heat; it is well known that in Papin's digeſter water may be made red hot by confinement, and will then diſſolve many bodies which otherwiſe are little or not at all acted upon by it. From hence it may be conceived, that under immenſe preſſure of ſuperincumbent materials, and by great heat, theſe maſſes of lava may have undergone a kind of aqueous ſolution, without any tendency to vitrification, and might thence have a power of cryſtallization, whence all the varieties above mentioned from the different proportion of the materials, or the different degrees of heat they may have undergone in this aqueous ſolution. And that the uniformity of the mixture of the original earths, as of lime, argil, ſilex, magneſia, and barytes, which they contain, was owing to their boiling together a longer or ſhorter time before their elevation into mountains. See note XIX. art. 8.
The ſeat of volcanos ſeems to be principally, if not entirely, in theſe ſtrata of granite; as many of them are ſituated on granite mountains, and throw up from time to time ſheets of lava which run down over the preceeding ſtrata from the ſame origin; and in this they ſeem to differ from the heat which has ſeparated the clay, coal, and ſand in moraſſes, which would appear to have riſen from a kind of fermentation, and thus to have pervaded the whole maſs without any expuition of lava.
[Page 65] All the lavas from Veſuvius contain one fourth part of iron, (Kirwan's Min.) and all the five primitive earths, viz. calcareous, argillaceous, ſiliceous, barytic, and magneſian earths, which are alſo evidently produced now daily from the recrements of animal and vegetable bodies. What is to be thence concluded? Has the granite ſtratum in very antient times been produced like the preſent calcareous and ſiliceous maſſes, according to the ingenious theory of Dr. Hutton, who ſays new continents are now forming at the bottom of the ſea to riſe in their turn, and that thus the terraqueous globe has been, and will be, eternal? Or ſhall we ſuppoſe that this internal heated maſs of granite, which forms the nucleus of the earth, was a part of the body of the ſun before it was ſeparated by an exploſion? Or was the fun originally a planet, inhabited like ours, and a ſatellite to ſome other greater fun, which has long been extinguiſhed by diffuſion of its light, and around which the preſent ſun continues to revolve, according to a conjecture of the celebrated Mr. Herſchell, and which conveys to the mind a moſt ſublime idea of the progreſſive and increaſing excellence of the works of the Creator of all things?
For the more eaſy comprehenſion of the facts and conjectures concerning the ſituation and production of the various ſtrata of the earth, I ſhall here ſubjoin a ſuppoſed ſection of the globe, but without any attempt to give the proportions of the parts, or the number of them, but only their reſpective ſituation over each other, and a geological recapitulation.
1. The earth was projected along with the other primary planets from the ſun, which is ſuppoſed to be on fire only on its ſurface, emitting light without much internal heat like a ball of burning camphor.
2. The rotation of the earth round its axis was occaſioned by its greater friction or adheſion to one ſide of the cavity from which it was ejected; and from this rotation it acquired its ſpheroidical form. As it cooled in its aſcent from the ſun its nucleus became harder; and its attendant vapours were condenſed, forming the ocean.
4. On this nucleus of granite and baſaltes, thus covered by the ocean, were formed the calcareous beds of limeſtone, marble, chalk, ſpar, from the exuviae of marine animals; with the flints, or chertz, which accompany them. And were ſtratified by their having been formed at different and very diſtant periods of time.
5. The whole terraqueous globe was burſt by central fires; iſlands and continents were raiſed, conſiſting of granite or lava in ſome parts, and of limeſtone in others; and great vallies were ſunk, into which the ocean retired.
[Page 66] 7. On ſome parts of theſe iſlands and continents of granite or limeſtone were gradually produced extenſive moraſſes from the recrements of vegetables and of land animals; and from theſe moraſſes, heated by fermentation, were produced clay, marle, ſandſtone, coal, iron, (with the baſes of variety of acids;) all which were ſtratified by their having been formed at different, and very diſtant periods of time.
8. In the elevation of the mountains very numerous and deep fiſſures neceſſarily were produced. In theſe fiſſures many of the metals are formed partly from deſcending materials, and partly from aſcending ones raiſed in vapour by ſubterraneous fires. In the fiſſures of granite or porphery quartz is formed; in the fiſſures of limeſtone calcareous ſpar is produced.
9. During theſe firſt great volcanic fires it is probable the atmoſphere was either produced, or much increaſed; a proceſs which is perhaps now going on in the moon; Mr. Herſchell having diſcovered a volcanic crater three miles broad burning on her diſk.
10. The ſummits of the new mountains were cracked into innumerable lozenges by the cold dews or ſnows falling upon them when red hot. From theſe ſummits, which were then twice as high as at preſent, cubes and lozenges of granite, and baſalt, and quartz in ſome countries, and of marble and flints in others, deſcended gradually into the valleys, and were rolled together in the beds of rivers, (which were then ſo large as to occupy the whole valleys, which they now only interſect;) and produced the great beds of gravel, of which many valleys conſiſt.
11. In ſeveral parts of the earth's ſurface ſubſequent earthquakes, from the fermentation of moraſſes, have at different periods of time deranged the poſition of the matters above deſcribed. Hence the gravel, which was before in the beds of rivers, has in ſome places been raiſed into mountains, along with clay and coal ſtrata which were formed from moraſſes and waſhed down from eminences into the beds of rivers or the neighbouring ſeas, and in part raiſed again with gravel or marine ſhells over them; but this has only obtained in few places compared with the general diſtribution of ſuch materials. Hence there ſeem to have exiſted two ſources of earthquakes, which have occurred at great diſtance of time from each other; one from the granite beds in the central parts of the earth, and the other from the moraſſes on its ſurface. All the ſubſequent earthquakes and volcanos of modern days compared with theſe are of ſmall extent and inſignificant effect.
12. Beſides the argillaceous ſand-ſtone produced from moraſſes, which is ſtratified with clay, and coal, and iron, other great beds of ſiliceous ſand have been formed in the ſea by the combination of an unknown acid from moraſſes, and the calcareous matters of the ocean.
13. The warm waters which are found in many countries, are owing to ſteam ariſing from great depths through the fiſſures of limeſtone or lava, elevated by ſubterranean fires, and condenſed between the ſtrata of the hills over them; and not from any decompoſition of pyrites or manganeſe near the ſurface of the earth.
Aquatic nymphs! you lead with viewleſs marchThe winged vapour up the aerial arch.CANTO III. l. 13.
1. THE atmoſphere will diſſolve a certain quantity of moiſture as a chemical menſtruum, even when it is much below the freezing point, as appears from the diminution of ice ſuſpended in froſty air, but a much greater quantity of water is evaporated and ſuſpended in the air by means of heat, which is perhaps the univerſal cauſe of fluidity, for water is known to boil with leſs heat in vacuo, which is a proof that it will evaporate faſter in vacuo, and that the air therefore rather hinders than promotes its evaporation in higher degrees of heat. The quick evaporation occaſioned in vacuo by a ſmall degree of heat is agreeably ſeen in what is termed a pulſe-glaſs, which conſiſts of an exhauſted tube of glaſs with a bulb at each end of it and with about two thirds of the cavity filled with alcohol, in which the ſpirit is inſtantly ſeen to boil by the heat of the finger-end applied on a bubble of ſteam in the lower bulb, and is condenſed again in the upper bulb by the leaſt conceivable comparative coldneſs.
2. Another circumſtance evincing that heat is the principal cauſe of evaporation is that at the time of water being converted into ſteam, a great quantity of heat is taken away from the neighbouring bodies. If a thermometer be repeatedly dipped in ether, or in rectified ſpirit of wine, and expoſed to a blaſt of air, to expedite the evaporation by perpetually removing the ſaturated air from it, the thermometer will preſently ſink below freezing. This warmth, taken from the ambient bodies at the time of evaporation by the ſteam, is again given out when the ſteam is condenſed into water. Hence the water in a worm-tub during diſtillation ſo ſoon becomes hot; and hence the warmth accompanying the deſcent of rain in cold weather.
3. The third circumſtance, ſhewing that heat is the principal cauſe of evaporation, is, that ſome of the ſteam becomes again condenſed when any part of the heat is withdrawn. Thus when warmer ſouth-weſt winds replete with moiſture ſucceed the colder northeaſt winds all bodies that are denſe and ſubſtantial, as ſtone walls, brick floors, &c. abſorb ſome of the heat from the paſſing air, and its moiſture becomes precipitated on them, while the north-eaſt winds become warmer on their arrival in this latitude, and are thence diſpoſed to take up more moiſture, and are termed drying winds.
4. Heat ſeems to be the principal cauſe of the ſolution of many other bodies, as common ſalt, or blue vitriol diſſolved in water, which when expoſed to ſevere cold are precipitated, or carried, to the part of the water laſt frozen; this I obſerved in a phial filled with a ſolution of blue vitriol which was frozen; the phial was burſt, the ice [Page 68] thawed, and a blue column of cupreous vitriol was left ſtanding upright on the bottom of the broken glaſs, as deſcribed in note XIX.
II. Hence water may either be diſſolved in air, and may then be called an aerial ſolution of water; or it may be diſſolved in the fluid matter of heat, according to the theory of M. Lavoiſier, and may then be called ſteam. In the former caſe it is probable there are many other vapours which may precipitate it, as marine acid gas, or fluor acid gas. So alcaline gas and acid gas diſſolved in air precipitate each other, nitrous gas precipitates vital air from its azote, and inflammable gas mixed with vital air ignited by an electric ſpark either produces or precipitates the water in both of them. Are there any ſubtle exhalations occaſionally diffuſed in the atmoſphere which may thus cauſe rain?
1. But as water is perhaps many hundred times more ſoluble in the fluid matter of heat than in air, I ſuppoſe the education of this heat, by whatever means it is occaſioned, is the principal cauſe of devaporation. Thus if a region of air is brought from a warmer climate, as the S. W. winds, it becomes cooled by its contact with the earth in this latitude, and parts with ſo much of its moiſture as was diſſolved in the quantity of calorique, or heat, which it now looſes, but retains that part which was ſuſpended by its attraction to the particles of air, or by aerial ſolution, even in the moſt ſevere froſts.
2. A ſecond immediate cauſe of rain is a ſtream of N. E. wind deſcending from a ſuperior current of air, and mixing with the warmer S. W. wind below; or the reverſe of this, viz. a ſuperior current of S. W. wind mixing with an inferior one of N. E. wind; in both theſe caſes the whole heaven becomes inſtantly clouded, and the moiſture contained in the S. W. current is precipitated. This cauſe of devaporation has been ingeniouſly explained by Dr. Hutton in the Tranſact. of Edinburgh, Vol. I. and ſeems to ariſe from this circumſtance; the particles of air of the N. E. wind educe part of the heat from the S. W. wind, and therefore the water which was diſſolved by that quantity of heat is precipitated; all the other part of the water, which was ſuſpended by its attraction to the particles of air, or diſſolved in the remainder of the heat, continues unprecipitated.
3. A third method by which a region of air becomes cooled, and in conſequence depoſits much of its moiſture, is from the mechanical expanſion of air, when part of the preſſure is taken off. In this caſe the expanded air becomes capable of receiving or attracting more of the matter of heat into its interſtices, and the vapour, which was previouſly diſſolved in this heat, is depoſited, as is ſeen in the receiver of an air-pump, which becomes dewy, as the air within becomes expanded by the education of part of it. See note VII. Hence when the mercury in the barometer ſinks without a change of the wind the air generally becomes colder. See note VII. on Elementary Heat. And it is probably from the varying preſſure of the incumbent air that in ſummer days ſmall black clouds are often thus ſuddenly produced, and again ſoon vaniſh. See a paper in Philos. Tranſ. Vol. LXXVIII. intitled Frigorific Experiments on the Mechanical Expanſion of Air.
[Page 69] 4. Another portion of atmoſpheric water may poſſibly be held in ſolution by the electric fluid, ſince in thunder ſtorms a precipitation of the water ſeems to be either the cauſe or the conſequence of the eduction of the electricity. But it appears more probable that the water is condenſed into clouds by the eduction of its heat, and that then the ſurplus of electricity prevents their coaleſcence into larger drops, which immediately ſucceeds the departure of the lightning.
5. The immediate cauſe why the barometer ſinks before rain is, firſt, becauſe a region of warm air, brought to us in the place of the cold air which it had diſplaced, muſt weigh lighter, both ſpecifically and abſolutely, if the height of the warm atmoſphere be ſuppoſed to be equal to that or the preceeding cold one. And ſecondly, after the drops of rain begin to fall in any column of air, that column becomes lighter, the falling drops only adding to the prſſure of the air in proportion to the reſiſtance which they meet with in paſſing through that fluid.
If we could ſuppoſe water to be diſſolved in air without heat, or in very low degrees of heat, I ſuppoſe the air would become heavier, as happens in many chemical ſolution, but if water diſſolved in the matter of heat, or calorique, be mixed with an aerial ſolutions, of water, there can be no doubt but an atmoſphere conſiſting of ſuch a mixture muſt become lighter in proportion to the quantity of calorique. On the ſame circumſtance depends the viſible vapour produced from the breath of animals in cold weather, or from a boiling kettle; the particles of cold air, with which it is mixed, ſteal a part of its heat, and become themſelves raiſed in temperature, whence part of the water is precipitated in viſible vapour, which, if in great quantity ſinks to the ground; if in ſmall quantity, and the ſurrounding air is not previouſly ſaturated, it ſpreads itſelf till it becomes again diſſolved.
Your lucid bands condenſe with fingers chillThe blue miſt hovering round the gelid hill.CANTO III. l. 19.
THE ſurface of the earth conſiſts of ſtrata many of which were formed originally beneath the ſea, the mountains were afterwards forced up by ſubterraneous fires, as appears from the fillures in the rocks of which they conſiſt the quantity of volcanic productions all over the world, and the numerous remains of craters of volcanos in mountainous countries. Hence the ſtrata which compoſe the ſides of mountains lie ſlanting downwards, and one or two or more of the external ſtrata not reaching to the ſummit when the mountain was raiſed up, the ſecond or third ſtratum or a more inferior one is there expoſed to day; this may be well repreſented by forceably thruſting a blunt inſtrument through ſeveral ſheets of paper, a bur will ſtand up with the lowermoſt ſheet ſtanding higheſt in the center of it. On this uppermoſt ſtratum, which is colder as it is more elevated, the dews are condenſed in large quantities; and ſliding down paſs under the firſt or ſecond or third ſtratum which compoſe the ſides of the hill; and either form a moraſs below, or a weeping rock, by oozing out in numerous places, or many of theſe leſs currents meeting together burſt out in a more copious rill.
The ſummits of mountains are much colder than the plains in their vicinity, owing to ſeveral cauſes; 1. Their being in a manner inſulated or cut off from the common heat of the earth, which is always of 48 degrees, and perpetually counteracts the effects of external cold beneath that degree. 2. From their ſurfaces being larger in proportion to their ſolid contents, and hence their heat more expeditiouſly carried away by the ever-moving atmoſphere. 3. The increaſing rarity of the air as the mountain riſes. All thoſe bodies which conduct electricity well or ill, conduct the matter of heat likewiſe well or ill. See note VII. Atmoſpheric air is a bad conductor of electricity and thence confines it on the body where it is accumulated, but when it is made very rare, as in the exhauſted receiver, the electric aura paſſes away immediately to any diſtance. The ſame circumſtance probably happens in reſpect to heat, which is thus kept by the denſer air on the plains from eſcaping, but is diſſipated on the hills where the air is thinner. 4. As the currents of air riſe up the ſides of mountains they become mechanically rarefied, the preſſure of the incumbent column leſſening as they aſcend. Hence the expanding air abſorbs heat from the mountain as it aſcends, as explained in note VII. 5. There is another, and perhaps more powerful cauſe, I ſuſpect, which may occaſion the great cold on mountains, and in the higher parts of the atmoſphere, and which has not yet been attended to; I mean that the fluid matter of heat may prodably gravitate round the earth, and form an atmoſphere on its ſurface, mixed with the aerial atmoſphere, which may diminiſh or become rarer, as it recedes from the earth's ſurface, in a greater proportion than the air diminiſhes.
[Page 71] 6. The great condenſation of moiſture on the ſummits of hills has another cauſe, which is the daſhing of moving clouds againſt them, in miſty days this is often ſeen to have great effect on plains, where an eminent tree by obſtructing the miſt as it moves along ſhall have a much greater quantity of moiſture drop from its leaves than falls at the ſame time on the ground in its vicinity. Mr. White, in his Hiſtory of Selborne gives an account of a large tree ſo ſituated, from which a ſtream flowed during a moving miſt ſo as to fill the cart-ruts in a lane otherwiſe not very moiſt, and ingeniouſly adds, that trees planted about ponds of ſtagnant water contribute much by theſe means to ſupply the reſervoir. The ſpherules which conſtitute a miſt or cloud are kept from uniting by ſo ſmall a power that a little agitation againſt the leaves of a tree, or the greater attraction of a flat moiſt ſurface, condenſes or precipitates them.
If a leaf has its ſurface moiſtened and particles of water ſeparate from each other as in a miſt be brought near the moiſtened ſurface of a leaf, each particle will be attracted more by that plain ſurface of water on the leaf than it can be by the ſurrounding particles of the miſt, becauſe globules only attract each other in one point, whereas a plain attracts a globule by a greater extent of its ſurface.
The common cold ſprings are thus formed on elevated grounds by the condenſed vapours, and hence are ſtronger when the nights are cold after hot days in ſpring, than even in the wet days of winter. For the warm atmoſphere during the day has diſſolved much more water than it can ſupport in ſolution during the cold of the night, which is thus depoſited in large quantities on the hills, and yet ſo gradually as to ſoak in between the ſtrata of them, rather than to ſlide off over their ſurfaces like ſhowers of rain. The common heat of the internal parts of the earth is aſcertained by ſprings which ariſe from ſtrata of earth too deep to be affected by the heat of ſummer or the froſts of winter. Thoſe in this country are of 48 degrees of heat, thoſe about Philidelphia were ſaid by Dr. Franklin to be 52; whether this variation is to be accounted for by the difference of the ſun's heat on that country, according to the ingenious theory of Mr. Kirwan, or to the vicinity of ſubterranean fires is not yet, I think, decided. There are however ſubterraneous ſtreams of water not exactly produced in this manner, as ſtreams iſſuing from fiſſures in the earth, communicating with the craters of old volcanoes; in the Peak of Derbyſhire are many hollows, called ſwallows, where the land floods ſink into the earth, and come out at ſome miles diſtant, as at Ilam near Aſhborne. See note on Fica, Vol. II.
Other ſtreams of cold water ariſe from beneath the ſnow on the Alps and Andes, and other high mountains, which is perpetualy thawing at its under ſurface by the common heat of the earth, and gives riſe to large rivers. For the origin of warm ſprings ſee note on Fucus, Vol. II.
You round Echinus ray his arrowy mail,Give the keel'd Nautilus his oar and ſail.Firm to his rock with ſilver cords ſuſpendThe anchor'd Pinna, and his Cancer-friend.CANTO III. l. 67.
THE armour of the Echinus, or Sea-hedge Hog, conſiſts generally of moveable ſpines; (Linnei Syſtem. Nat. Vol. I. p. 1102.) and in that reſpect reſembles the armour of the land animal of the ſame name. The irregular protuberances on other ſea-ſhells, as on ſome ſpecies of the Purpura, and Murex, ſerve them as a fortification againſt the attacks of their enemies.
It is ſaid that this animal foreſees tempeſtuous weather, and ſinking to the bottom of the ſea adheres firmly to ſea-plants, or other bodies by means of a ſubſtance which reſembles the horns of ſnails. Above twelve hundred of theſe fillets have been counted by which this animal fixes itſelf; and when afloat, it contracts theſe fillets between the baſes of its points, the number of which often amounts to two thouſand. Dict. raiſonne. art. Ourſin. de mer.
There is a kind of Nautilus, called by Linneus, Argonauta, whoſe ſhell has but one cell; of this animal Pliny affirms, that having exonerated its ſhell by throwing out the water, it ſwims upon the ſurface, extending a web of wonderful tenuity, and bending back two of its arms and rowing with the reſt, makes a ſail, and at length receiving the water dives again. Plin. IX. 29. Linneus adds to his deſcription of this animal, that like the the Crab Diogenes or Bernhard, it occupies a houſe not its own, as it is not connected to its ſhell, and is therefore foreign to it; who could have given credit to this if it had not been atteſted by ſo many who have with their own eyes ſeen this argonaut in the act of ſailing? Syſt. Nat. p. 1161.
The Nautilus, properly ſo named by Linneus, has a ſhell conſiſting of many chambers, of which cups are made in the Eaſt with beautiful painting and carving on the mother-pearl. The animal is ſaid to inhabit only the uppermoſt or open chamber, which is larger than the reſt; and that the reſt remain empty except that the pipe, or ſiphunculus, which communicates from one to the other of them is filled with an appendage of the animal like a gut or ſtring. Mr. Hook in his Philos. Exper. p. 306, imagines this to be a dilatable or compreſſible tube, like the air-bladders of fiſh, and that by contracting or permitting it to expand, it renders its ſhell boyant or the contrary. See Note on Ulva, Vol. II.
The Pinna, or Sea-wing, is contained in a two-valve ſhell, weighing ſometimes fifteen pounds, and emits a beard of fine long gloſſy ſilk-like fibres, by which it is ſuſpended to the rocks twenty or thirty feet beneath the ſurface of the ſea. In this ſituation it is ſo ſucceſsfully attacked by the eight-footed Polypus, that the ſpecies perhaps could not exiſt [Page 73] but for the exertions of the Cancer Pinnotheris, who lives in the ſame ſhell as a guard and companion. Amoen. Academ. Vol. II. p. 48. Lin. Syſt. Nat. Vol. I. p. 1159, and p. 1040.
The Pinnotheris, or Pinnophylax, is a ſmall crab naked like Bernard the Hermit, but is furniſhed with good eyes, and lives in the ſame ſhell with the Pinna; when they want food the Pinna opens its ſhell, and ſends its faithful ally to forage; but if the Cancer ſees the Polypus, he returns ſuddenly to the arms of his blind hoſteſſs, who by cloſing the ſhell avoids the fury of her enemy; otherwiſe, when it has procured a booty, it brings it to the opening of the ſhell, where it is admitted, and they divide the prey. This was obſerved by Haſlequiſt in his voyage to Paleſtine.
The Byſſus of the antients, according to Ariſtotle, was the beard of the Pinna above mentioned, but ſeems to have been uſed by other writers indiſcriminately for any ſpun material, which was eſteemed finer or more valuable than wool. Reaumur ſays the threads of this Byſſus are not leſs fine or leſs beautiful than the ſilk, as it is ſpun by the ſilk-worm; the Pinna on the coaſts of Italy and Provence (where it is fiſhed up by ironhooks fixed on long poles) is called the ſilk-worm of the ſea. The ſtockings and gloves manufactured from it, are of exquiſite fineneſs, but too warm for common wear, and are thence eſteemed uſeful in rhumatiſm and gout. Dict. Raiſonné art. Pinne-marine. The warmth of the Byſſus, like that of ſilk, is probably owing to their being bad conductors of heat, as well as of electricity. When theſe fibres are broken by violence, this animal as well as the muſcle has the power to reproduce them like the common ſpiders, as was obſerved by M. Adanſon. As raw ſilk, and raw cobwebs, when ſwallowed, are liable to produce great ſickneſs (as I am informed) it is probable the part of muſcles, which ſometimes diſagrees with the people who eat them, may be this ſilky web, by which they attach themſelves to ſtones. The large kind of Pinna contains ſome mother-pearl of a reddiſh tinge, according to M. d'Argenville. The ſubſtance ſold under the name of Indian weed, and uſed at the bottom of fiſh-lines, is probably a production of this kind, which however is ſcarcely to be diſtinguiſhed by the eye from the tendons of a rat's tail, after they have been ſeparated by putrefaction in water, and well cleaned and rubbed; a production, which I was once ſhewn as a great curioſity; it had the uppermoſt bone of the tail adhering to it, and was ſaid to have been uſed as an ornament in a lady's hair.
With worm-like beard his toothleſs lips array,And teach the unweildy Sturgeon to betray.CANTO III. l. 71.
THE Sturgeon, Acipenſer, Strurio. Lin. Syſt. Nat. Vol. I. p. 403. is a fiſh of great curioſity as well as of great importance; his mouth is placed under the head, without teeth, like the opening of a purſe, which he has the power to puſh ſuddenly out or retract. Before this mouth under the beak or noſe hang four tendrils ſome inches long, and which ſo reſemble earth-worms that at firſt ſight they may be miſtaken for them. This clumſy toothleſs fiſh is ſuppoſed by this contrivance to keep himſelf in good condition, the ſolidity of his fleſh evidently ſhewing him to be a fiſh of prey. He is ſaid to hide his large body amongſt the weeds near the ſea-coaſt, or at the mouths of large rivers, only expoſing his cirrhi or tendrils, which ſmall fiſh or ſea-inſects miſtaking for real worms approach for plunder, and are ſucked into the jaws of their enemy. He has been ſuppoſed by ſome to root into the ſoil at the bottom of the ſea or rivers; but the cirrhi, or tendrills abovementioned, which hang from his ſnout over his mouth, muſt themſelves be very inconvenient for this purpoſe, and as it has no jaws it evidently lives by ſuction, and during its reſidence in the ſea a quantity of ſea-inſects are found in its ſtomach.
The fleſh was ſo valued in the time of the Emperor Severus, that it was brought to table by ſervants with coronets on their heads, and preceded by muſic, which might give riſe to its being in our country preſented by the Lord Mayor to the King. At preſent it is caught in the Danube, and the Walga, the Don, and other large rivers for various purpoſes. The ſkin makes the beſt covering for carriages; iſinglaſs is prepared from parts of the ſkin; cavear from the ſpawn; and the fleſh is pickled or ſalted, and ſent all over Europe.
Who with fine films, ſuſpended o'er the deep,Of Oil effuſive lull the waves to ſleep.CANTO III. l. 87.
THERE is reaſon to believe that when oil is poured upon water, the two ſurfaces do not touch each other, but that the oil is ſuſpended over the water by their mutual repulſion. This ſeems to be rendered probable by the following experiment: if one drop of oil be droped on a baſon of water, it will immediately diffuſe itſelf over the whole, for there being no friction between the two ſurfaces, there is nothing to prevent its ſpreading itſelf by the gravity of the upper part of it, except its own tenacity, into a pellicle [Page 75] of the greateſt tenuity. But if a ſecond drop of oil be put upon the former, it does not ſpread itſelf, but remains in the form of a drop, as the other already occupied the whole ſurface of the baſon, and there is friction in oil paſſing over oil, though none in oil paſſing over water.
Hence when oil is diffuſed on the ſurface of water gentle breezes have no influence in raiſing waves upon it; for a ſmall quantity of oil will cover a very great ſurface of water, (I ſuppoſe a ſpoonful will diffuſe itſelf over ſome acres) and the wind blowing upon this carries it gradually forwards; and there being no friction between the two ſurfaces the water is not affected. On which account oil has no effect in ſtilling the agitation of the water after the wind ceaſes, as was found by the experiments of Dr. Franklin.
This circumſtance lately brought into notice by Dr. Franklin had been mentioned by Pliny, and is ſaid to be in uſe by the divers for pearls, who in windy weather taken down with them a little oil in their mouths, which they occaſionally give out when the inequality of the ſupernatant waves prevents them from ſeeing ſufficiently diſtinctly for their purpoſe.
The wonderful tenuity with which oil can be ſpread upon water is evinced by a few drops projected from a bridge, where the eye is properly placed over it, paſſing through all the priſmatic colours as it diffuſes itſelf. And alſo from another curious experiment of Dr. Franklin's: he cut a piece of cork to about the ſize of a letter-wafer, leaving a point ſtanding off like a tangent at one edge of the circle. This piece of cork was then dipped in oil and thrown into a large pond of water, and as the oil flowed off at the point, the cork-wafer continued to revolve in a contrary direction for ſeveral minutes. The oil flowing off all that time at the pointed tangent in coloured ſtreams. In a ſmall pond of water this experiment does not ſo well ſucceed, as the circulation of the cork ſtops as ſoon as the water becomes covered with the pellicle of oil. See Additional Note, No. XIII. and Note on Fucus, Vol. II.
The eaſe with which oil and water ſlide over each other is agreeably ſeen if a phial be about half filled with equal parts of oil and water, and made to oſcillate ſuſpended by a ſtring, the upper ſurface of the oil and the lower one of the water will always keep ſmooth; but the agitation of the ſurfaces where the oil and water meet, is curious; for their ſpecific gravities being not very different, and their friction on each other nothing, the higheſt ſide of the water, as the phial deſcends in its oſcillation, having acquired a greater momentum than the loweſt ſide (from its having deſcended further) would riſe the higheſt on the aſcending ſide of the oſcillation, and thence puſhes the then uppermoſt part of the water amongſt the oil.
Meet fell Teredo, as he mines the keelWith beaked head, and break his lips of ſteel.CANTO III. l. 91.
THE Teredo, or ſhip-worm, has two calcareous jaws, hemiſpherical, flat before, and angular behind. The ſhell is taper, winding, penetrating ſhips and ſubmarine wood, and was brought from India into Europe, Linnei Syſtem. Nat. p. 1267. The Tarieres, or ſea-worms, attack and erode ſhips with ſuch fury, and in ſuch numbers, as often greatly to endanger them. It is ſaid that our veſſels have not known this new enemy above fifty years, that they were brought from the ſea about the Antilles to our parts of the ocean, where they have increaſed prodigiouſly. They bore their paſſage in the direction of the fibres of the wood, which is their nouriſhment, and cannot return or paſs obliquely, and thence when they come to a knot in the wood, or when two of them meet together with their ſtony mouths, they periſh for want of food.
In the years 1731 and 1732 the United Provinces were under a dreadful alarm concerning theſe inſects, which had made great depredation on the piles which ſupport the banks of Zeland, but it was happily diſcovered a few years afterwards that theſe inſects had totally abandoned that iſland, (Dict. Raiſonné, art. Vers Rongeurs,) which might have been occaſioned by their not being able to live in that latitude when the winter was rather ſeverer than uſual.
Turn the broad helm, the fluttering canvas urgeFrom Maelſtrom's fierce innavigable ſurge.CANTO III. l. 93.
ON the coaſt of Norway there is an extenſive vortex, or eddy, which lies between the iſlands of Moſkoe and Moſkenas, and is called Moſkoeſtrom, or Maelſtrom; it occupies ſome leagues in circumference, and is ſaid to be very dangerous and often deſtructive to veſſels navigating theſe ſeas. It is not eaſy to underſtand the exiſtence of a conſtant deſcending ſtream without ſuppoſing it muſt paſs through a ſubterranean cavity to ſome other part of the earth or ocean which may lie beneath its level; as the Mediterranean ſeems to lie beneath the level of the Atlantic ocean, which therefore [Page 77] conſtantly flows into it through the Straits; and the waters of the Gulph of Mexico lie much above the level of the ſea about the Floridas and further northward, which gives riſe to the Gulph-ſtream, as deſcribed in note on Caſſia in Vol. II.
The Maelſtrom is ſaid to be ſtill twice in about twenty-four hours when the tide is up, and moſt violent at the oppoſite times of the day. This is not difficult to account for, ſince when ſo much water is brought over the ſubterraneous paſſage, if ſuch exiſts, as compleatly to fill it and ſtand many feet above it, leſs diſturbance muſt appear on the ſurface. The Maelſtrom is deſcribed in the Memoires of the Swediſh Academy of Sciences, and Pontoppiden's Hiſt. of Norway, and in Univerſal Muſeum for 1763, p. 131.
The reaſon why eddies of water become hollow in the middle is becauſe the water immediately over the centre of the well, or cavity, falls faſter, having leſs friction to oppoſe its deſcent, than the water over the circumference or edges of the well. The circular motion or gyration of eddies depends on the obliquity of the courſe of the ſtream, or to the friction or oppoſition to it being greater on one ſide of the well than the other; I have obſerved in water paſſing through a hole in the bottom of a trough, which was always kept full, the gyration of the ſtream might be turned either way by increaſing the oppoſition of one ſide of the eddy with ones finger, or by turning the ſpout, through which the water was introduced, a little more obliquely to the hole on one ſide or on the other. Lighter bodies are liable to be retained long in eddies of water, while thoſe rather heavier than water are ſoon thrown out beyond the circumference by their acquired momentum becoming greater than that of the water. Thus if equal portions of oil and water be put into a phial, and by means of a ſtring be whirled in a circle round the hand, the water will always keep at the greater diſtance from the centre, whence in the eddies formed in rivers during a flood a perſon who endeavours to keep above water or to ſwim is liable to be detained in them, but on ſuffering himſelf to ſink or dive he is ſaid readily to eſcape. This circulation of water in deſcending through a hole in a veſſel Dr. Franklin has ingeniouſly applied to the explanation of hurricanes or eddies of air.
While round dark crags impriſon'd waters bendThrough rifted ice, in ivory veins deſcend.CANTO III. l. 113.
THE common heat of the interior parts of the earth being always 48 degrees, both in winter and ſummer, the ſnow which lies in contact with it is always in a thawing ſtate; Hence in ice-houſes the external parts of the collection of ice is perpetually thawing and thus preſerves the internal part of it; ſo that it is neceſſary to lay up many tons for the preſervation of one ton. Hence in Italy conſiderable rivers have their ſource from beneath the eternal glaciers, or mountains of ſnow and ice.
In our country when the air in the courſe of a froſt continues a day or two at very near 32 degrees, the common heat of the earth thaws the ice on its ſurface, while the thermometer remains at the freezing point. This circumſtance is often obſervable in the rimy mornings of ſpring; the thermometer ſhall continue at the freezing point, yet all the rime will vaniſh, except that which happens to lie on a bridge, a board, or on a cake of cow-dung, which being thus as it were inſulated or cut off from ſo free a communication with the common heat of the earth by means of the air under the bridge, or wood, or dung, which are bad conductors of heat, continues ſome time longer unthawed. Hence when the ground is covered thick with ſnow, though the froſt continues, and the ſun does not ſhine, yet the ſnow is obſerved to decreaſe very ſenſibly. For the common heat of the earth melts the under ſurface of it, and the upper one evaporates by its ſolution in the air. The great evaporation of ice was obſerved by Mr. Boyle, which experiment I repeated ſome time ago. Having ſuſpended a piece of ice by a wire and weighed it with care without touching it with my hand, I hung it out the whole of a clear froſty night, and ſound in the morning it had loſt nearly a fifth of its weight. Mr. N. Wallerius has ſince obſerved that ice at the time of its congelation evaporates faſter than water in its fluid form; which may be accounted for from the heat given out at the inſtant of freezing; (Sauſſure's Eſſais ſur Hygromet. p. 249.) but this effect is only momentary.
Thus the vegetables that are covered with ſnow are ſeldom injured; ſince, as they lie between the thawing ſnow, which has 32 degrees of heat, and the covered earth which has 48, they are preſerved in a degree of heat between theſe; viz. in 40 degrees of heat. Whence the moſs on which the rein-deer feed in the northern latitudes vegetates beneath the ſnow; (See note on Muſchus, Vol. II.) and hence many Lapland and Alpine plants periſhed through cold in the botanic garden at Upſal, for in their native ſituations, though the cold is much more intenſe, yet at its very commencement they are covered deep with ſnow, which remains till late in the ſpring. For this fact ſee Amaenit. Academ. Vol. I. No. 48. In our climate ſuch plants do well covered with dried fern, under which they will grow, and even flower, till the ſevere vernal froſts ceaſe. For the increaſe of glaciers ſee Note on Canto I. l. 529.
While ſouthern gales o'er weſtern oceans roll,And Eurus ſteas his ice-winds from the pole.CANTO IV. l. 15
THE theory of the winds is yet very imperfect, in part perhaps owing to the want of obſervations ſufficiently numerous of the exact times and places where they begin and ceaſe to blow, but chiefly to our yet imperfect knowledge of the means by which great regions of air are either ſuddenly produced or ſuddenly deſtroyed.
The air is perpetually ſubject to increaſe or diminution from its combination with other bodies, or its evolution from them. The vital part of the air, called oxygene, is continually produced in this climate from the perſpiration of vegetables in the ſunſhine, and probably from the action of light on clouds or on water in the tropical climates, where the ſun has greater power, and may exert ſome yet umknown laws of luminous combination. Another part of the atmoſphere, which is called azote, is perpetually ſet at liberty from animal and vegetable bodies by putrefaction or combuſtion, from many ſprings of water, from volatile alcali, and probably from fixed alcali, of which there is an exhauſtleſs ſource in the water of the ocean. Both theſe component parts of the air are perpetually again diminiſhed by their contact with the ſoil, which covers the ſurface of the earth, producing nitre. The oxygene is diminiſhed in the production of all acids, of which the carbonic and muriatic exiſt in great abundance. The azote is diminiſhed in the growth of animal bodies, of which it conſtitutes an important part, and in its combinations with many other natural productions.
They are both probably diminiſhed in immenſe quantities by uniting with the inflammable air, which ariſes from the mud of rivers and lakes at ſome ſeaſons, when the atmoſphere is light: the oxgene of the air producing water, and the azote producing volatile alcali by their combinations with this inflammable air. At other ſeaſons of the year theſe principles may again change their combinations, and the atmoſpheric air be reproduced.
Mr. Lavoiſier found that one pound of charcoal in burning conſumed two pounds nine ounces of vital air, or oxygene. The conſumption of vital air in the proceſs of making red lead may readily be reduced to calculation; a ſmall barrel contains about twelve hundred weight of this commodity, 1200 pounds of lead by calcination abſorb about 144 pounds of vital air; now as a cubic foot of water weighs 1000 averdupois ounces, and as vital air is above 800 times lighter than water, it follows that every barrel of red lead contains nearly 2000 cubic feet of vital air. If this can be performed in miniature in a ſmall oven, what may not be done in the immenſe elaboratories of nature!
Theſe great elaboratories of nature include almoſt all her foſſil as well as her animal and vegetable productions. Dr. Prieſtley obtained air of greater or leſs purity, both [Page 80] vital and azotic, from almoſt all the foſſil ſubſtances he ſubjected to experiment. Four ounce-weight of lava from Iceland heated in an earthen retort yielded twenty ounce-meaſures of air.
In this account the fixed air was previouſly extracted from the limeſtones by acids, and the heat applied was much leſs than was neceſſary to extract all the air from the bodies employed. Add to this the known quantities of air which are combined with the calciform ores, as the ochres of iron, manganeſe, calamy, grey ore of lead, and ſome idea may be formed of the great production of air in volcanic eruptions, as mentioned in note on Chunda, Vol. II. and of the perpetual abſorptions and evolutions of whole oceans of air from every part of the earth.
But there would ſeem to be an officina aeris, a ſhop where air is both manufactured and deſtroyed in the greateſt abundance within the polar circles, as will hereafter be ſpoken of. Can this be effected by ſome yet unknown law of the congelation of aqueous or ſaline fluids, which may ſet at liberty their combined heat, and convert a part both of the acid and alcali of ſea-water into their component airs? Or on the contrary can the electricity of the northern lights convert inflammable air and oxygene into water, whilſt the great degree of cold at the poles unites the azote with ſome other baſe? Another officina aeris, or manufacture of air, would ſeem to exiſt within the tropics or at the line, though in a much leſs quantity than at the poles, owing perhaps to the action of the ſun's light on the moiſture ſuſpended in the air, as will alſo be ſpoken of hereafter; but in all other parts of the earth theſe abſorptions and evolutions of air in a greater or leſs degree are perpetually going on in inconceivable abundance; increaſed probably, and diminiſhed at different ſeaſons of the year by the approach or retroceſſion of the ſun's light; future diſcoveries muſt elucidate this part of the ſubject. To this ſhould be added [Page 81] that as heat and electricity, and perhaps magnetiſm, are known to diſplace air, that it is not impoſſible but that the increaſed or diminiſhed quantities of theſe fluids diffuſed in the atmoſphere may increaſe its weight a well as its bulk; ſince their ſpecific attractions or affinities to matter are very ſtrong, they probably alſo poſſeſs general gravitation to the earth; a ſubject which wants further inveſtigation. See Note XXVI.
The velocity of the ſurface of the earth in moving round its axis diminiſhes from the equator to the poles. Whence if a region of air in this country ſhould be ſuddenly removed a few degrees towards the north it muſt conſtitute a weſtern wind, becauſe from the velocity it had previouſly acquired in this climate by its friction with the earth it would for a time move quicker than the ſurface of the country it was removed to; the contrary muſt enſue when a region of air is tranſported from this country a few degrees ſouthward, becauſe the velocity it had acquired in this climate would be leſs than that of the earth's ſurface where it was removed to, whence it would appear to conſtitute a wind from the eaſt, while in reality the eminent parts of the earth would be carried againſt the too ſlow air. But if this tranſportation of air from ſouth to north be performed gradually, the motion of the wind will blow in the diagonal between ſouth and weſt. And on the contrary if a region of air be gradually removed from north to ſouth it would alſo blow diagonally between the north and eaſt, from whence we may ſafely conclude that all our winds in this country which blow from the north or eaſt, or any point between them, conſiſt of regions of air brought from the north; and that all our winds blowing from the ſouth or weſt, or from any point between them, are regions of air brought from the ſouth.
It frequently happens during the vernal months that after a north-eaſt wind has paſſed over us for ſeveral weeks, during which time the barometer has ſtood at above 30 ½ inches, it becomes ſuddenly ſucceeded by a ſouth-weſt wind, which alſo continues ſeveral weeks, and the barometer ſinks to nearly 28 ½ inches. Now as two inches of the mercury in the barometer balance one-fifteenth part of the whole atmoſphere, an important queſtion here preſents itſelf, what is become of all this air.
1. This great quantity of air can not be carried in a ſuperior current towards the line, while the inferior current flows towards the poles, becauſe then it would equally affect the barometer, which ſhould not therefore ſubſide from 30 ½ inches to 28 ½ for ſix weeks together.
2. It cannot be owing to the air having loſt all the moiſture which was previouſly diſſolved in it, becauſe theſe warm ſouth-weſt winds are replete with moiſture, and the cold north-eaſt winds, which weigh up the mercury in the barometer to 31 inches, conſiſt of dry air.
3. It can not be carried over the polar regions and be accumulated on the meridian oppoſite to us in its paſſage towards the line, as ſuch an accumulation would equal one-fifteenth of the whole atmoſphere, and can not be ſuppoſed to remain in that ſituation for ſix weeks together,
[Page 82] 4. It can not depend on the exiſtence of tides in the atmoſphere, ſince it muſt then correſpond to lunar periods. Nor to accumulations of air from the ſpecific levity of the upper regions of the atmoſphere, ſince its degree of fluidity muſt correſpond with its tenuity, and conſequently ſuch great mountains of air can not be ſuppoſed to exiſt for ſo many weeks together as the ſouth-weſt winds ſometimes continue.
5. It remains therefore that there muſt be at this time a great and ſudden abſorption of air in the polar circle by ſome unknown operation of nature, and that the ſouth wind runs in to ſupply the deficiency. Now as this ſouth wind conſiſts of air brought from a part of the earth's ſurface which moves faſter than it does in this climate it muſt have at the ſame time a direction from the weſt by retaining part of the velocity it had previouſly acquired. Theſe ſouth-weſt winds coming from a warmer country, and becoming colder by their contact with the earth of this climate, and by their evpanſion, (ſo great a part of the ſuperincumbent atmoſphere having vaniſhed,) precipitate their moiſture; and as they continue for ſeveral weeks to be abſorbed in the polar circle would ſeem to receive a perpetual ſupply from the tropical regions, eſpecially over the line, as will hereafter be ſpoken of.
It may ſometimes happen that a north-eaſt wind having paſſed over us may be bent down and driven back before it has acquired any heat from the climate, and may thus for a few hours or a day have a ſouth-weſt direction, and from its deſcending from a higher region of the atmoſphere may poſſeſs a greater degree of cold than an inferior north-eaſt current of air.
The extreme cold of Jan. 13, 1709, at Paris came on with a gentle ſouth wind, and was diminiſhed when the wind changed to the north, which is accounted for by Mr. Homberg from a reflux of air which had been flowing for ſome time from the north. Chemical Eſſays by R. Watſon, Vol. V. p. 182.
It may happen that a north-eaſt current may for a day or two paſs over us and produce inceſſant rain by mixing with the inferior ſouth-weſt current; but this as well as the former is of ſhort duration, as its friction will ſoon carry the inferior current along with it, and dry or froſty weather will then ſucceed.
The north-eaſt winds of this country conſiſt of regions of air from the north, travelling ſometimes at the rate of about a mile in two minutes during the vernal months for ſeveral weeks together from the polar regions toward the ſouth, the mercury in the barometer ſtanding above 30. Theſe winds conſiſt of air greatly cooled by the evaporation of the ice and ſnow over which it paſſes, and as they become warmer by their contact with the earth of this climate are capable of diſſolving more moiſture as they paſs along, and are thence attended with froſts in winter and with dry hot weather in ſummer.
1. This great quantity of air can not be ſupplied by ſuperior currents paſſing in a contrary direction from ſouth to north, becauſe ſuch currents muſt as they ariſe into the atmoſphere a mile or two high become expoſed to ſo great cold as to occaſion them [Page 83] to depoſit their moiſture, which would fall through the inferior current upon the earth in ſome part of their paſſage.
2. The whole atmoſphere muſt have increaſed in quantity, becauſe it appears by the barometer that there exiſts one-fifteenth part more air over us for many weeks together, which could not be thus accumulated by difference of temperature in reſpect to heat, or by any aeroſtatic laws at preſent known, or by any lunar influence.
From whence it would appear that immenſe maſſes of air were ſet at liberty from their combinations with ſolid bodies, along with a ſufficient quantity of combined heat, within the polar circle, or in ſome region to the north of us; and that they thus perpetually increaſe the quantity of the atmoſphere; and that this is again at certain times re-abſorbed, or enters into new combinations at the line or tropical regions. By which wonderful contrivance the atmoſphere is perpetually renewed and rendered fit for the ſupport of animal and vegetable life.
The ſouth-eaſt winds of this country conſiſt of air from the north which had paſſed by us, or over us, and before it had obtained the velocity of the earth's ſurface in this climate had been driven back, owing to a deficiency of air now commencing at the polar regions. Hence theſe are generally dry or freezing winds, and if they ſucceed north-eaſt winds ſhould prognoſticate a change of wind from north-eaſt to ſouth-weſt; the barometer is generally about 30. They are ſometimes attended with cloudy weather, or rain, owing to their having acquired an increaſed degree of warmth and moiſture before they became retrograde; or to their being mixed with air from the ſouth.
2. Sometimes theſe ſouth-eaſt winds conſiſt of a vertical eddy of north-eaſt air, without any mixture of ſouth-weſt air; in that caſe the barometer continues above 30, and the weather is dry or froſty for four or five days together.
It ſhould here be obſerved, that air being an elaſtic fluid muſt be more liable to eddies than water, and that theſe eddies muſt extend into cylinders or vortexes of greater diameter, and that if a vertical eddy of north-eaſt air be of ſmall diameter or has paſſed but a little way to the ſouth of us before its return, it will not have gained the velocity of the earth's ſurface to the ſouth of us, and will in conſequence become a ſouth-eaſt wind.—But if the vertical eddy be of large diameter, or has paſſed much to the ſouth of us, it will have acquired velocity from its friction with the earth's ſurface to the ſouth of us, and will in conſequence on its return become a ſouth-weſt wind, producing great cold.
There ſeem to be three ſources of the north-weſt winds of this hemiſphere of the earth. 1. When a portion of ſouthern air, which was paſſing over us, is driven back by accumulation of new air in the polar regions. In this cafe I ſuppoſe they are generally moiſt or rainy winds, with the barometer under 30, and if the wind had previouſly been in the ſouth-weſt, it would ſeem to prognoſticate a change to the north-eaſt.
[Page 84] 2. If a current of north wind is paſſing over us but a few miles high, without any eaſterly direction; and is bent down upon us, it muſt immediately poſſeſs a weſterly direction, becauſe it will now move faſter than the ſurface of the earth where it arrives; and thus becomes changed from a north-eaſt to a north-weſt wind. This deſcent of a north-eaſt current of air producing a north-weſt wind may continue ſome days with clear or freezing weather, as it may be ſimply owing to a vertical eddy of north-eaſt air, as will be ſpoken of below. It may otherwiſe be forced down by a current of ſouth-weſt wind paſſing over it, and in this caſe it will be attended with rain for a few days by the mixture of the two airs of different degrees of heat; and will prognoſticate a change of wind from north-eaſt to ſouth-weſt if the wind was previouſly in the north-eaſt quarter.
3. On the eaſtern coaſt of North America the north-weſt winds bring froſt, as the north-eaſt winds do in this country, as appears from variety of teſtimony. This ſeems to happen from a vertical ſpiral eddy made in the atmoſphere between the ſhore and the ridge of mountains which form the ſpine or back-bone of that continent. If a current of water runs along the hypothenuſe of a triangle an eddy will be made in the included angle, which will turn round like a water-wheel as the ſtream paſſes in contact with one edge of it. The ſame muſt happen when a ſheet of air flowing along from the north-eaſt riſes from the ſhore in a ſtraight line to the ſummit of the Apalachian mountains, a part of the ſtream of north-eaſt air will flow over the mountains, another part will revert and circulate ſpirally between the ſummit of the country and the eaſtern ſhore, continuing to move toward the ſouth; and thus be changed from a north-eaſt to a north-weſt wind.
This vertical ſpiral eddy having been in contact with the cold ſummits of theſe mountains, and deſcending from higher parts of the atmoſphere will loſe part of its heat, and thus conſtitute one cauſe of the greater coldneſs of the eaſtern ſides of North America than of the European ſhores oppoſite to them, which is ſaid to be equal to twelve degrees of north latitude, which is a wonderful fact, not otherwiſe eaſy to be explained, ſince the heat of the ſprings at Philadelphia is ſaid to be 52, which is greater than the medium heat of the earth in this country.
The exiſtence of vertical eddies, or great cylinders of air rolling on the ſurface of the earth, is agreeable to the obſervations of the conſtructors of windmills; who on this idea place the area of the fails leaning backwards, inclined to the horizon; and believe that then they have greater power than when they are placed quite perpendicularly. The ſame kind of rolling cylinders of water obtain in rivers owing to the friction of the water againſt the earth at their bottoms; as is known by bodies having been obſerved to float upon their ſurfaces quicker than when immerſed to a certain depth. Theſe vertical eddies of air probably exiſt all over the earth's ſurface, but particularly at the bottom or ſides of mountains; and more ſo probably in the courſe of the ſouth-weſt than of the north-eaſt winds; becauſe the former fall from an eminence, as it were, on a part of the earth where there is a deficiency of the quantity of air; as is ſhewn by the ſinking of the barometer: whereas the latter are puſhed or [Page 85] ſqueezed forward by an addition to the atmoſphere behind them, as appears by the riſing of the barometer.
Now as the ſun paſſes twice over the equator for once over either tropic, the equator has not time to become cool; and on this account it is in general hotter at the line than at the tropics; and therefore the air over the line, except in ſome few inſtances hereafter to be mentioned, continues to aſcend at all ſeaſons of the year, preſſed upwards by regions of air brought from the tropics.
This air thus brought from the tropics to the equator, would conſtitute a north wind on one ſide of the equator, and a ſouth wind on the other; but as the ſurface of the earth at the equator moves quicker than the ſurface of the earth at the tropics, it is evident that a region of air brought from either tropic to the equator, and which had previouſly only acquired the velocity of the earth's ſurface at the tropics, will now move too flow for the earth's ſurface at the equator, and will thence appear to move in a direction contrary to the motion of the earth. Hence the trade-winds, though they conſiſt of regions of air brought from the north on one ſide of the line, and from the ſouth on the other, will appear to have the diagonal direction of north-eaſt and ſouth-weſt winds.
Now it is commonly believed that there are ſuperior currents of air paſſing over theſe north-eaſt and ſouth-weſt currents in a contrary direction, and which deſcending near the tropics produce vertical whirlpools of air. An important queſtion here again preſents itſelf, What becomes of the moiſture which this heated air ought to depoſit, as it cools in the upper regions of the atmoſphere in its journey to the tropics? It has been ſhewn by Dr. Prieſtley and Mr. Ingenhouz that the green matter at the bottom of ciſterns, and the freſh leaves of plants immerſed in water, give out conſiderable quantities of vital air in the ſun-ſhine; that is, the perſpirable matter of plants (which is water much divided in its egreſs from their minute pores) becomes decompoſed by the ſun's light, and converted into two kinds of air, the vital and inflammable airs. The moiſture contained or diſſolved in the aſcending heated air at the line muſt exiſt in great tenuity; and by being expoſed to the great light of the ſun in that climate, the water may be decompoſed, and the new airs ſpread on the atmoſphere from the line to the poles.
2. From the obſervations of M. Bougner on the mountain Pinchinca, one of the Cordelieres immediately under the line, there appears to be no condenſible vapour above three or four miles high. Now though the atmoſphere at that height may be cold to a very conſiderable degree; yet its total deprivation of condenſible vapour would ſeem to ſhew, that its water was decompoſed; as there are no experiments to evince that any degree of cold hitherto known has been able to deprive air of its moiſture; and great [Page 86] abundance of ſnow is depoſited from the air that flows to the polar regions, though it is expoſed to no greater degrees of cold in its journey thither than probably exiſts at four miles height in the atmoſphere at the line.
3. The hygrometer of Mr. Sauſſure alſo pointed to dryneſs as he aſcended into rarer air; the ſingle hair of which it was conſtructed, contracting from deficiency of moiſture. Eſſais ſur l'Hygromet. p. 143.
From theſe obſervations it appears either that rare and cold air requires more moiſture to ſaturate it than denſe air; or that the moiſture becomes decompoſed and converted into air, as it aſcends into there cold and rare regions of the atmoſphere.
1. In the Arabian and Indian ſeas are winds, which blow fix months one way, and ſix months the other, and are called Monſoons; by the accidental diſpoſitions of land and ſea it happens, that in ſome places the air near the tropic is ſuppoſed to become warmer when the ſun is vertical over it, than at the line. The air in theſe places conſequently aſcends preſſed upon one ſide by the north-eaſt regions of air, and on the other ſide by the ſouth-weſt regions of air. For as the air brought from the ſouth has previouſly obtained the velocity of the earth's ſurface at the line, it moves faſter than the earth's ſurface near the tropic where it now arrives, and becomes a ſouth-weſt wind, while the air from the north becomes a north-eaſt wind as before explained. Theſe two winds do not ſo quietly join and aſcend as the north-eaſt and ſouth-eaſt winds, which meet at the line with equal warmth and velocity and form the trade-winds; but as they meet in contrary directions before they aſcend, and cannot be ſuppoſed accurately to balance each other, a rotatory motion will be produced as they aſcend like water falling through a hole, and an horizontal or ſpiral eddy is the conſequence; theſe eddies are more or leſs rapid, and are called Tornadoes in their moſt violent ſtate, raiſing water from the ocean in the weſt or ſand from the deſerts of the eaſt, in leſs violent degrees they only mix together the two currents of north-eaſt and ſouth-weſt air, and produce by this means inceſſant rains, as the air of the north-eaſt acquires ſome of the heat from the ſouth-weſt wind, as explained in Note XXV. This circumſtance of the eddies produced by the monſoon-winds was ſeen by Mr. Bruce in Abyſſinia; he relates that for many ſucceſſive mornings at the commencement of the rainy monſoon, he obſerved a cloud of apparently ſmall dimenſions whirling round with great rapidity, and in a few minutes the heavens became covered with dark clouds with conſequent great rains. See Note on Canto III. l. 125.
2. But it is not only at the place where the air aſcends at the northern extremity of the rainy monſoon, and where it forms tornadoes, as obſerved above by Mr. Bruce, but over a great tract of country ſeveral degrees in length in certain parts as in the Arabian ſea, a perpetual rain for ſeveral months deſcends, ſimilar to what happens for weeks together in our own climate in a leſs degree during the ſouth-weſt winds. Another important [Page 87] queſtion preſents itſelf here, If the climate to which this ſouth-weſt wind arrives, is not colder than that it comes from, why ſhould it depoſit its moiſture during its whole journey? if it be a colder climate, why does it come thither? The tornadoes of air above deſcribed can extend but a little way, and it is not eaſy to conceive that a ſuperior cold current of air can mix with an inferior one, and thus produce ſhowers over ten degrees of country, ſince at about three miles high there is perpetual froſt; and what can induce theſe narrow and ſhallow currents to flow over each other ſo many hundred miles?
Though the earth at the northren extremity of this monſoon may be more heated by certain circumſtances of ſituation than at the line, yet it ſeems probable that the intermediate country between that and the line, may continue colder than the line (as in other parts of the earth) and hence that the air coming from the line to ſupply this aſcent or deſtruction of air at the northern extremity of the monſoon will be cooled all the way in its approach, and in conſequence depoſit its water. It ſeems probable that at the northern extremity of this monſoon, where the tornadoes or hurricanes exiſt, that the air not only aſcends but is in part converted into water, or otherwiſe diminiſhed in quantity, as no account is given of the exiſtence of any ſuperior currents of it.
As the ſouth-weſt winds are always attended with a light atmoſphere, an incipient vacancy, or a great diminution of air muſt have taken place to the northward of them in all parts of the earth wherever they exiſt, and a depoſition of their moiſture ſucceeds their being cooled by the climate they arrive at, and not by a contrary current of cold air over them, ſince in that caſe the barometer would not ſink. They may thus in our own country be termed monſoons without very regular periods.
3. Another cauſe of TORNADOES independent of the monſoons is ingeniouſly explained by Dr. Franklin; when in the tropical countries a ſtratum of inferior air becomes ſo heated by its contact with the warm earth, that its expanſion is increaſed more than is equivalent to the preſſure of the ſtratum of air over it; or when the ſuperior ſtratum becomes more condenſed by cold than the inferior one by preſſure, the upper region will deſcend and the lower one aſcend. In this ſituation if one part of the atmosphere be hotter from ſome fortuitous circumſtances, or, has leſs preſſure over it, the lower ſtratum will begin to aſcend at this part, and reſemble water falling through a hole as mentioned above. If the lower region of air was going forwards with conſiderable velocity, it will gain an eddy by riſing up this hole in the incumbent heavy air, ſo that the whirlpool or tornado has not only its progreſſive velocity, but its circular one alſo, which thus lifts up or overturns every thing within its ſpiral whirl. By the weaker whirlwinds in this country the trees are ſometimes thrown down in a line of only twenty or forty yards in breadth, making a kind of avenue through a country. In the Weſt Indies the ſea riſes like a cone in the whirl, and is met by black clouds produced by the cold upper air and the warm lower air being rapidly mixed; whence are produced the great and ſudden rains called water-ſpouts; while the upper and lower airs exchange their plus or minus electricity in perpetual lightenings.
The ſea being a tranſparent maſs is leſs heated at its ſurface by the ſun's rays than the land, and its continual change of ſurface contributes to preſerve a greater uniformity in the heat of the air which hangs over it. Hence the ſurface of the tropical iſlands is more heated during the day than the ſea that ſurrounds them, and cools more in the night by its greater elevation: whence in the afternoon when the lands of the tropical iſlands have been much heated by the ſun, the air over them aſcends preſſed upwards by the cooler air of the incircling ocean, in the morning again the land becoming cooled more than the ſea, the air over it deſcends by its increaſed gravity, and blows over the ocean near its ſhores.
1. There are various irregular winds beſides thoſe above deſcribed, which conſiſt of horizontal or vertical eddies of air owing to the inequality of the earth's ſurface, or the juxtapoſition of the ſea. Other irregular winds have their origin from increaſed evaporation of water, or its ſudden devaporation and deſcent in ſhowers; others from the partial expanſion and condenſation of air by heat and cold; by the accumulation or defect of electric fluid, or to the air's new production or abſorption occaſioned by local cauſes not yet diſcovered. See Notes VII. and XXV.
2. There ſeem to exiſt only two original winds: one conſiſting of air brought from the north, and the other of air brought from the ſouth. The former of theſe winds has alſo generally an apparent direction from the eaſt, and the latter from the weſt, ariſing from the different velocities of the earth's ſurface. All the other winds above deſcribed are deflections or retrogreſſions of ſome parts of theſe currents of air from the north or ſouth.
3. One fifteenth part of the atmoſphere is occaſionally deſtroyed, and occaſionally reproduced by unknown cauſes. Theſe cauſes are brought into immediate activity over a great part of the ſurface of the earth at nearly the ſame time, but always act more powerful to the northward than to the ſouthward of any given place; and would hence ſeem to have their principal effect in the polar circles, exiſting nevertheleſs though with leſs power toward the tropics or at the line.
For when the north-eaſt wind blows the barometer riſes, ſometimes from 28 ½ inches to 30 ½, which ſhews a great new generation of air in the north; and when the ſouthweſt wind blows the barometer ſinks as much, which ſhews a great deſtruction of air in the north. But as the north-eaſt winds ſometimes continue for five or ſix weeks, the newly-generated air muſt be deſtroyed at thoſe times in the warmer climates to the ſouth of us, or circulate in ſuperior currents, which has been ſhewn to be improbable from its not depoſiting its water. And as the ſouth-weſt winds ſometimes continue for ſome weeks, there muſt be a generation of air to the ſouth at thoſe times, or ſuperior currents, which laſt has been ſhewn to be improbable.
4. The north-eaſt winds being generated about the poles are puſhed forwards towards the tropics or line, by the preſſure from behind, and hence they become warmer, as [Page 89] explained in Note VII. as well as by their coming into contact with a warmer part of the earth which contributes to make theſe winds greedily abſorb moiſture in their paſſage. On the contrary, the ſouth-weſt winds, as the atmoſphere is ſuddenly diminiſhed in the polar regions, are drawn as it were into an incipient vacancy, and become therefore expanded in their paſſage, and thus generate cold, as explained in Note VII. and are thus induced to part with their moiſture, as well as by their contact with a colder part of the earth's ſurface. Add to this, that the difference in the ſound of the north-eaſt and ſouth-weſt winds may depend on the former being puſhed forwards by a preſſure behind, and the latter falling as it were into a partial or incipient vacancy before; whence the former becomes more condenſed, and the latter more rarefied as it paſſes. There is a whiſtle, termed a lark-call, which conſiſts of a hollow cylinder of tin-plate, cloſed at each end, about half an inch in diameter and a quarter of an inch high, with oppoſite holes about the ſize of a gooſe-quill through the centre of each end; if this lark-whiſtle be held between the lips the ſound of it is manifeſtly different when the breath is forceably blown through it from within outwards, and when it is ſucked from without inwards. Perhaps this might be worthy the attention of organ-builders.
5. A ſtop is put to this new generation of air, when about a fifteenth of the whole is produced, by its increaſing preſſure; and a ſimilar boundary is fixed to its abſorption or deſtruction by the decreaſe of atmoſpheric preſſure. As water requires more heat to convert it into vapour under a heavy atmoſphere than under a light one, ſo in letting off the water from muddy fiſh-ponds great quantities of air-bubbles are ſeen to aſcend from the bottom, which were previouſly confined there by the preſſure of the water. Similar bubbles of inflammable air are ſeen to ariſe from lakes in many ſeaſons of the year, when the atmoſphere ſuddenly becomes light.
6. The increaſed abſorptions and evolutions of air muſt, like its ſimple expanſions, depend much on the preſence or abſence of heat and light, and will hence, in reſpect to the times and places of its production and deſtruction, be governed by the approach or retroceſſion of the ſun, and on the temperature, in regard to heat, of various latitudes, and parts of the ſame latitude, ſo well explained by Mr. Kirwan.
7. Though the immediate cauſe of the deſtruction or reproduction of great maſſes of air at certain times, when the wind changes from north to ſouth, or from ſouth to north can not yet be aſcertained; yet as there appears greater difficulty in accounting for this change of wind for any other known cauſes, we may ſtill ſuſpect that there exiſts in the arctic and antarctic circles a BEAR or DRAGON yet unknown to philoſophers, which at times ſuddenly drinks up, and as ſuddenly at other times vomits out one-fifteenth part of the atmoſphere: and hope that this or ſome future age will learn how to govern and domeſticate a monſter which might be rendered of ſuch important ſervice to mankind.
IF along with the uſual regiſters of the weather obſervations were made on the winds in many parts of the earth with the three following inſtruments, which might be conſtructed at no great expence, ſome uſeful information might be acquired.
[Page 90] 1. To mark the hour when the wind changes from north-eaſt to ſouth-weſt, and the contrary. This might be managed by making a communication from the vane of a weathercock to a clock; in ſuch a manner, that if the vane ſhould revolve quite round, a tooth on its revolving axis ſhould ſtop the clock, or put back a ſmall bolt on the edge of a wheel revolving once in twenty-four hours.
2. To diſcover whether in a year more air paſſed from north to ſouth, or the contrary. This might be effected by placing a windmill-ſail of copper about nine inches diameter in a hollow cylinder about ſix inches long, open at both ends, and fixed on an eminent ſituation exactly north and ſouth. Thence only a part of the north-eaſt and ſouth-weſt currents would affect the ſail ſo as to turn it; and if its revolutions were counted by an adapted machinery, as the ſail would turn one way with the north currents of air, and the contrary one with the ſouth currents, the advance of the counting finger either way would ſhew which wind had prevailed moſt at the end of the year.
NORTH-EAST WINDS conſiſt of air flowing from the north, where it ſeems to be occaſionally produced; has an apparent direction from the eaſt owing to its not having acquired in its journey the increaſing velocity of the earth's ſurface; theſe winds are analogous to the trade-winds between the tropics, and frequently continue in the vernal months for four and ſix weeks together, with a high barometer, and fair or froſty weather. 2. They ſometimes conſiſt of ſouth-weſt air, which had paſſed by us or over us, driven back by a new accumulation of air in the north. Theſe continue but a day or two, and are attended with rain. See Note XXV.
SOUTH-WEST WIND conſiſts of air flowing from the ſouth, and ſeems occaſionally abſorbed at its arrival to the more northern latitudes. It has a real direction from the weſt owing to its not having loſt in its journey the greater velocity it had acquired from the earth's ſurface from whence it came. Theſe winds are analogous to the monſoons between the tropics, and frequently continue for four or ſix weeks together, with a low barometer and rainy weather. 2. They ſometimes conſiſt of north-eaſt air, which had paſſed by us or over us, which becomes retrograde by a commencing deficiency of air in the north. Theſe winds continue but a day or two, attended with ſeverer froſt with a ſinking barometer; their cold being increaſed by their expanſion, as they return, into an incipient vacancy.
NORTH-WEST WINDS conſiſt, firſt, of ſouth-weſt winds, which have paſſed over us, bent down and driven back towards the ſouth by newly generated northern air. They continue but a day or two, and are attended with rain or clouds. 2. They conſiſt of north-eaſt winds bent down from the higher parts of the atmoſphere, and having there acquired a greater velocity than the earth's ſurface; are froſty or fair. 3. They conſiſt of north-eaſt winds formed into a vertical ſpiral eddy, as on the eaſtern coaſts of North America, and bring ſevere froſt.
[Page 91] SOUTH-EAST WINDS conſiſt, firſt, of north-eaſt winds become retrograde, continue for a day or two, froſty or fair, ſinking barometer. 2. They conſiſt of north-eaſt winds formed into a vertical eddy not a ſpiral one, froſt or fair.
NORTH WINDS conſiſt, firſt, of air flowing ſlowly from the north, ſo that they acquire the velocity of the earth's ſurface as they approach, are fair or froſty, ſeldom occur. 2. They conſiſt of retrograde ſouth winds; theſe continue but a day or two, are preceded by ſouth-weſt winds; and are generally ſucceeded by north-eaſt winds, cloudy or rainy, barometer riſing.
SOUTH WINDS conſiſt, firſt, of air flowing ſlowly from the ſouth, looſing their previous weſtern velocity by the friction of the earth's ſurface as they approach, moiſt, ſeldom occur. 2. They conſiſt of retrograde north winds; theſe continue but a day or two, are preceded by north-eaſt winds, and generally ſucceeded by ſouth-weſt winds, colder, barometer ſinking.
EAST WINDS conſiſt of air brought haſtily from the north, and not impelled farther ſouthward, owing to a ſudden beginning abſorption of air in the northern regions, very cold, barometer high, generally ſucceeded by ſouth-weſt wind.
WEST WINDS conſiſt of air brought haſtily from the ſouth, and checked from proceeding further to the north by a beginning production of air in the northern regions, warm and moiſt, generally ſucceeded by north-eaſt wind. 2. They conſiſt of air bent down from the higher regions of the atmoſphere, if this air be from the ſouth, and brought haſtily it becomes a wind of great velocity, moving perhaps 60 miles an hour, is warm and rainy; if it conſiſts of northern air bent down it is of leſs velocity and colder.
Dec. 1, 1790. The barometer ſunk ſuddenly, and the wind, which had been ſome days north-eaſt with froſt, changed to ſouth-eaſt with an inceſſant though moderate fall of ſnow. A part of the northern air, which had paſſed by us I ſuppoſe, now became retrograde before it had acquired the velocity of the earth's ſurface to the ſouth of us, and being attended by ſome of the ſouthern air in its journey, the moiſture of the latter became condenſed and frozen by its mixture mith the former.
Dec. 2, 3. The wind changed to north-weſt and thawed the ſnow. A part of the ſouthern air, which had paſſed by us or over us, with the retrograde northern air above deſcribed, was now in its turn driven back, before it had loſt the velocity of the ſurface of the earth to the ſouth of us, and conſequently became a north-weſt wind; and not having loſt the warmth it brought from the ſouth produced a thaw.
Dec. 4, 5. Wind changed to north-eaſt with froſt and a riſing barometer. The air from the north continuing to blow, after it had driven back the ſouthern air as above deſcribed, became a north-eaſt wind, having leſs velocity than the ſurface of the earth in this climate, and produced froſt from its coldneſs.
[Page 92] Dec. 6, 7. Wind now changed to the ſouth-weſt with inceſſant rain and a ſinking barometer. From unknown cauſes I ſuppoſe the quantity of air to be diminiſhed in the polar regions, and the ſouthern air cooled by the earth's ſurface, which was previouſly frozen, depoſits its moiſture for a day or two; afterwards the wind continued ſouth-weſt without rain, as the ſurface of the earth became warmer.
March 18, 1785. There has been a long froſt; a few days ago the barometer ſunk to 29 ½, and the froſt became more ſevere. Becauſe the air being expanded by a part of the preſſure being taken off became colder. This day the mercury roſe to 30, and the froſt ceaſed, the wind continuing as before between north and eaſt. March 19. Mercury above 30, weather ſtill milder, no froſt, wind north-eaſt. March 20. The ſame, for the mercury riſing ſhews that the air becomes more compreſſed by the weight above▪ and in conſequence gives out warmth.
April 4, 5. Froſt, wind north-eaſt, the wind changed in the middle of the day to the north-weſt without rain, and has done ſo for three or four days, becoming again north-eaſt at night. For the ſun now giving greater degrees of heat, the air aſcends as the ſun paſſes the zenith, and is ſupplied below by the air on the weſtern ſide as well as on the eaſtern ſide of the zenith during the hot part of the day; whence for a few hours, on the approach of the hot part of the day, the air acquires a weſterly direction in this longitude. If the north-weſt wind had been cauſed by a retrograde motion of ſome ſouthern air, which had paſſed over us, it would have been attended with rain or clouds.
April 10. It rained all day yeſterday, the wind north-weſt, this morning there was a ſharp froſt. The evaporation of the moiſture, (which fell yeſterday) occaſioned by the continuance of the wind, produced ſo much cold as to freeze the dew.
May 12. Frequent ſhowers with a current of colder wind preceding every ſhower. The ſinking of the rain or cloud preſſed away the air from beneath it in its deſcent, which having been for a time ſhaded from the ſun by the floating cloud, became cooled in ſome degree.
June 20. The barometer ſunk, the wind became ſouth-weſt, and the whole heaven was inſtantly covered with clouds. A part of the incumbent atmoſphere having vaniſhed, as appeared by the ſinking of the barometer, the remainder became expanded by its elaſticity, and thence attracted ſome of the matter of heat from the vapour intermixed with it, and thus in a few minutes a total devaporation took place, as in exhauſting the receiver of an air-pump. See note XXV. At the place where the air is deſtroyed, currents both from the north and ſouth flow in to ſupply the deficiency, (for it has been ſhewn that there are no other proper winds but theſe two) and the mixture of theſe winds produces ſo ſudden condenſation of the moiſture, both by the coldneſs of the northern air and the expanſion of both of them, that lightning is given out, and an incipient tornado takes place; whence thunder is ſaid frequently to approach againſt the wind.
Auguſt 28, 1732. Barometer was at 31, and Dec. 30, in the ſame year, it was at 28 2-tenths. Medical Eſſays, Edinburgh, Vol. II. p. 7. It appears from theſe journals that the mercury at Edinburgh varies ſometimes nearly three inches, or one tenth of [Page 93] the whole atmoſphere. From the journals kept by the Royal Society at London it appears ſeldom to vary more than two inches, or one-fifteenth of the whole atmoſphere. The quantity of the variation is ſaid ſtill to decreaſe nearer the line, and to increaſe in the more northern latitudes; which much confirms the idea that there exiſts at certain times a great deſtruction or production of air within the polar circle.
July 2, 1732. The weſterly winds in the journal in the Medical Eſſays, Vol. II. above referred to, are frequently marked with the number three to ſhew their greater velocity, whereas the eaſterly winds ſeldom approach to the number two. The greater velocity of the weſterly winds than the eaſterly ones is well known I believe in every climate of the world; which may be thus explained from the theory above delivered. 1. When the air is ſtill, the higher parts of the atmoſphere move quicker than thoſe parts which touch the earth, becauſe they are at a greater diſtance from the axis of motion. 2. The part of the atmoſphere where the north or ſouth wind comes from is higher than the part of it where it comes to, hence the more elevated parts of the atmoſphere continue to deſcend towards the earth as either of thoſe winds approach. 3. When ſouthern air is brought to us it poſſeſſes a weſterly direction alſo, owing to the velocity it had previouſly acquired from the earth's ſurface; and if it conſiſts of air from the higher parts of the atmoſphere deſcending nearer the earth, this weſterly velocity becomes increaſed. But when northern air is brought to us, it poſſeſſes an apparent eaſterly direction alſo, owing to the velocity which it had previouſly acquired from the earth's ſurface being leſs than that of the earth's ſurface in this latitude; now if the north-eaſt wind conſiſts of air deſcending from higher parts of the atmoſphere, this deficiency of velocity will be leſs, in conſequence of the ſame cauſe, viz. The higher parts of the atmoſphere deſcending, as the wind approaches, increaſes the real velocity of the weſtern winds, and decreaſes the apparent velocity of the eaſtern ones.
October 22. Wind changed from ſouth-eaſt to ſouth-weſt. There is a popular prognoſtication that if the wind changes from the north towards the ſouth paſſing through the eaſt, it is more likely to continue in the ſouth, than if it paſſes through the weſt, which may be thus accounted for. If the north-eaſt wind changes to a north-weſt wind, it ſhews either that a part of the northern air deſcends upon us in a ſpiral eddy, or that a ſuperior current of ſouthern air is driven back; but if a north-eaſt wind be changed into a ſouth-eaſt wind it ſhews that the northern air is become retrograde, and that in a day or two, as ſoon as that part of it has paſſed, which has not gained the velocity of the earth's ſurface in this latitude, it will become a ſouth wind for a few hours, and then a ſouth-weſt wind.
The writer of this imperfect ſketch of anemology wiſhes it may incite ſome perſon of greater leizure and ability to attend to this ſubject, and by comparing the various meteorological journals and obſervations already publiſhed, to conſtruct a more accurate and methodical treatiſe on this intereſting branch of philoſophy.
And wed the enamoured Oxygene to Light.CANTO IV. l. 34.
WHEN points or hairs are put into ſpring-water, as in the experiments of Sir B. Thompſon, (Philoſ. Tranſ. Vol. LXXVII.) and expoſed to the light of the ſun, much air, which looſely adhered to the water, riſes in bubbles, as explained in note on Fucus, Vol. II. A ſtill greater quantity of air, and of a purer kind, is emitted by Dr. Prieſtley's green matter, and by vegetable leaves growing in water in the ſun-ſhine, according to Mr. Ingenhouze's experiments; both which I ſuſpect to be owing to a decompoſition of the water perſpired by the plant, for the edge of a capillary tube of great tenuity may be conſidered as a circle of points, and as the oxygene, or principle of vital air, may be expanded into a gas by the ſun's light; the hydrogene or inflammable air may be detained in the pores of the vegetable.
Hence plants growing in the ſhade are white, and become green by being expoſed to the ſun's light; for their natural colour being blue, the addition of hydrogene adds yellow to this blue, and tans them green. I ſuppoſe a ſimilar circumſtance takes place in animal bodies; their perſpirable matter as it eſcapes in the ſun-ſhine becomes decompoſed by the edges of their pores as in vegetables, though in leſs quantity, as their perſpiration is leſs, and by the hydrogene being retained the ſkin becomes tanned yellow. In proof of this it muſt be obſerved that both vegetable and animal ſubſtances become bleached white by the ſun-beams when they are dead, as cabbage-ſtalks, bones, ivory, tallow, bees-wax, linen and cotton cloth; and hence I ſuppoſe the copper-coloured natives of ſunny countries might become etiolated or blanched by being kept from their infancy in the dark, or removed for a few generations to more northerly climates.
It is probable that on a ſunny morning much pure air becomes ſeparated from the dew by means of the points of vegetables on which it adheres, and much inflammable air imbibed by the vegetable, or combined with it; and by the ſun's light thus decompoſing water the effects of it in bleaching linen ſeems to depend (as deſcribed in Note X.): the water is decompoſed by the light at the ends or points of the cotton or thread, and the vital air unites with the phlogiſtic or colouring matters of the cloth, and produces a new acid, which is either itſelf colourleſs or waſhes out, at the ſame time the inflammable part of the water eſcapes. Hence there ſeems a reaſon why cotton bleaches ſo much ſooner than linen, viz. becauſe its fibres are three or four times ſhorter, and therefore protrude ſo many more points, which ſeem to facilitate the liberation of the vital air from the inflammable part of the water.
Bee's wax becomes bleached by expoſure to the ſun and dews in a ſimilar manner as metals become calcined or ruſty, viz. by the water on their ſurface being decompoſed; and hence the inflammable material which cauſed the colour becomes united with vital air forming a new acid, and is waſhed away.
[Page 95] Oil cloſe ſtopped in a phial not full, and expoſed long to the ſun's light, becomes bleached, as I ſuppoſe, by the decompoſition of the water it contains; the inflammable air riſing above the ſurface, and the vital air uniting with the colouring matter of the oil. For it is remarkable, that by ſhutting up a phial of bleached oil in a dark drawer, it in a little time becomes coloured again.
The following experiment ſhews the power of light in ſeparating vital air from another baſis, viz. from azote. Mr. Scheel inverted a glaſs veſſel filled with colourleſs nitrous acid into another glaſs containing the ſame acid, and on expoſing them to the ſun's light, the inverted glaſs became partly filled with pure air, and the acid at the ſame time became coloured. Scheel in Crell's Annal. 1786. But if the veſſel of colourleſs nitrous acid be quite full and ſtopped, ſo that no ſpace is left for the air produced to expand itſelf into, no change of colour takes place. Prieſtley's Exp. VI. p. 344. See Keir's very excellent Chemical Dictionary, p. 99. new edition.
A ſun-flower three feet and half high according to the experiment of Dr. Hales, perſpired two pints in one day (Vegetable Statics.) which is many times as much in proportion to its ſurface, as is perſpired from the ſurface and lungs of animal bodies; it follows that the vital air liberated from the ſurfaces of plants by the ſunſhine muſt much exceed the quantity of it abſorbed by their reſpiration, and that hence they improve the air in which they live during the light part of the day, and thus blanched vegetables will ſooner become tanned into green by the ſun's light, than etiolated animal bodies will become tanned yellow by the ſame means.
It is hence evident, that the curious diſcovery of Dr. Prieſtley, that his green vegetable matter and other aquatic plants gave out vital air when the ſun ſhone upon them, and the leaves of other plants did the ſame when immerſed in water, as obſerved by Mr. Ingenhouze, refer to the perſpiration of vegetables not to their reſpiration. Becauſe Dr. Prieſtley obſerved the pure air to come from both ſides of the leaves and even from the ſtalks of a water-flag, whereas one ſide of the leaf only ſerves the of the office of lungs, and certainly not the ſtalks. Exper. on Air, Vol. III. And thus in reſpect to the circumſtance in which plants and animals ſeemed the furthereſt removed from each other, I mean in their ſuppoſed mode of reſpiration, by which one was believed to purify the air which the other had injured, they ſeem to differ only in degree, and the analogy between them remains unbroken.
Plants are ſaid by many writers to grow much faſter in the night than in the day; as is particularly obſervable in ſeedlings at their riſing out of the ground. This probably is a conſequence of their ſleep rather than of the abſence of light; and in this I ſuppoſe they alſo reſemble animal bodies.
While in bright veins the ſilvery ſap aſcends.CANTO IV. l. 419.
AS buds are the viviparous offspring of vegetables, it becomes neceſſary that they ſhould be furniſhed with placental veſſels for their nouriſhment, till they acquire lungs or leaves for the purpoſe of elaborating the common juices of the earth into nutriment. Theſe veſſels exiſt in bulbs and in ſeeds, and ſupply the young plant with a ſweet juice till it acquires leaves, as is ſeen in converting barley into malt, and appears from the ſweet taſte of onions and potatoes, when they begin to grow.
The placental veſſels belonging to the buds of trees are placed about the roots of moſt, as the vine; ſo many roots are furniſhed with ſweet or mealy matter as fern-root, bryony, carrot, turnip, potatoe, or in the alburnum or ſap-wood as in thoſe trees which produce manna, which is depoſited about the month of Auguſt, or in the joints of ſugar cane, and graſſes; early in the ſpring the abſorbent mouths of theſe veſſels drink up moiſture from the earth, with a ſaccharine matter lodged for that purpoſe during the preceding autumn, and puſh this nutritive fluid up the veſſels of the alburnum to every individual bud, as is evinced by the experiments of Dr. Hales, and of Mr. Walker in the Edinburgh Philoſophical Tranſact. The former obſerved that the ſap from the ſtump of a vine, which he had cut off in the beginning of April, aroſe twenty-one feet high in tubes affixed to it for that purpoſe, but in a few weeks it ceaſed to bleed at all, and Dr. Walker marked the progreſs of the aſcending ſap, and found likewiſe that as ſoon as the leaves became expanded the ſap ceaſed to riſe; the aſcending juice of ſome trees is ſo copious and ſo ſweet during the ſap-ſeaſon that it is uſed to make wine, as the birch, betula, and ſycamore, acer pſeudo-platinus, and particularly the palm.
During this aſcent of the ſap-juice each individual leaf-bud expands its new leaves, and ſhoots down new roots, covering by their intertexture the old bark with a new one; and as ſoon as theſe new roots (or bark) are capable of abſorbing ſufficient juices from the earth for the ſupport of each bud, and the new leaves are capable of performing their office of expoſing theſe juices to the influence of the air; the placental veſſels ceaſe to act, coaleſce, and are tranſformed from ſap-wood, or alburnum, into inert wood; ſerving only for the ſupport of the new tree, which grows over them.
Thus from the pith of the new bud of the horſe-cheſnut five veſſels paſs out through the circle of the placental veſſels above deſcribed, and carry with them a minuter circle of thoſe veſſels; theſe five bundles of veſſels unite after their exit, and form the footſtalk or petiole of the new five-fingered leaf, to be ſpoken of hereafter. This ſtructure is well ſeen by cutting off a leaf of the horſe-cheſnut (Aeſculus Hippocaſtanum) in September before it falls, as the buds of this tree are ſo large that the flower may be ſeen in them with the naked eye.
[Page 97] After a time, perhaps about midſummer, another bundle of veſſels paſſes from the pith through the alburnum or ſap-veſſels in the boſom of each leaf, and unites by the new bark with the leaf, which becomes either a flower-bud or a leaf-bud to be expanded in the enſuing ſpring, for which purpoſe an apparatus of placental veſſels are produced with proper nutriment during the progreſs of the ſummer and autumn, and thus the vegetable becomes annually increaſed, ten thouſand buds often exiſting on one tree, according to the eſtimate of Linneus. Phil. Bot.
The vaſcular connection of vegetable buds with the leaves in whoſe boſoms they are formed is confirmed by the following experiment, (Oct. 20, 1781.) On the extremity of a young bud of the Mimoſa (ſenſitive plant) a ſmall drop of acid of vitriol was put by means of a pen, and, after a few ſeconds, the leaf in whoſe axilla it dwelt cloſed and opened no more, though the drop of vitriolic acid was ſo ſmall as apparently only to injure the ſummit of the bud. Does not this ſeem to ſhew that the leaf and its bud have connecting veſſels though they ariſe at different times and from different parts of the medulla or pith? And, as it exiſts previouſly to it, that the leaf is the parent of the bud?
This placentation of vegetable buds is clearly evinced from the ſweetneſs of the riſing ſap, and from its ceaſing to riſe as ſoon as the leaves are expanded, and thus compleats the analogy between buds and bulbs. Nor need we wonder at the length of the umbilical cords of buds ſince that muſt correſpond with their ſituation on the tree, in the ſame manner as their lymphatics and arteries are proportionally elongated.
It does not appear probable that any umbilical artery attends theſe placental abſorbents, ſince, as there ſeems to be no ſyſtem of veins in vegetables to bring back the blood from the extremities of their arteries, (except their pulmonary veins,) there could not be any vegetable fluids to be returned to their placenta, which in vegetables ſeems to be ſimply an organ for nutrition, whereas the placenta of the animal foetus ſeems likewiſe to ſerve as a reſpiratory organ like the gills of fiſhes.
And refluent blood in milky eddies bends.CANTO IV. l. 420.
THE individuality of vegetable buds was ſpoken of before, and is confirmed by the method of raiſing all kinds of trees by Mr. Barnes. (Method of propagating Fruit Trees. 1759. Lond. Baldwin.) He cut a branch into as many pieces as there were buds or leaves upon it, and wiping the two wounded ends dry he quickly applied to each a cement, previouſly warmed a little, which conſiſted principally of pitch, and planted them in the earth. The uſe of this cement I ſuppoſe to conſiſt in its preventing the bud from bleeding to death, though the author aſcribes it to its antiſceptic quality.
Theſe buds of plants, which are thus each an individual vegetable, in many circumſtances reſemble individual animals, but as animal bodies are detached from the earth, and move from place to place in ſearch of food, and take that food at conſiderable intervals of time, and prepare it for their nouriſhment within their own bodies after it is taken, it is evident they muſt require many organs and powers which are not neceſſary to a ſtationary bud. As vegetables are immoveably fixed to the ſoil from whence they draw their mouriſhment ready prepared, and this uniformly not at returning intervals, it follows that in examining their anatome we are not to look for muſcles of locomotion, as arms and legs; nor for organs to receive and prepare their nouriſhment, as a ſtomach and bowels; nor for a reſervoir for it after it is prepared, as a general ſyſtem of veins, which in locomotive animals contains and returns the ſuperfluous blood which is left after the various organs of ſecretion have been ſupplied, by which contrivance they are enabled to live a long time without new ſupplies of food.
The parts which we may expect to find in the anatome of vegetables correſpondent to thoſe in the animal economy are, 1. A ſyſtem of abſorbent veſſels to imbibe the moiſture of the earth ſimilar to the lacteal veſſels, as in the roots of plants; and another ſyſtem of abſorbents ſimilar to the lymphatics of animal bodies, opening its mouths on the internal cells and external ſurfaces of vegetables; and a third ſyſtem of abſorbent veſſels correſpondent with thoſe of the placentation of the animal foetus. 2. A pulmonary ſyſtem correſpondent to the lungs or gills of quadrupeds and fiſh, by which the fluid abſorbed by the lacteals and lymphatics may be expoſed to the influence of the air, this is done by the green leaves of plants, thoſe in the air reſembling lungs, and thoſe in the water reſembling gills; and by the petals of flowers. 3. Arterial ſyſtems to convey the fluid thus elaborated to the various glands of the vegetable for the purpoſes of its growth, nutrition, and various ſecretions. 4. The various glands which ſeparate from the vegetable blood the honey, wax, gum, reſin, ſtarch, ſugar, eſſential oil, &c. 5. The organs adapted for their propagation or reproduction. 6. Muſcles to perform ſeveral motions of their parts.
[Page 99] I. The exiſtence of that branch of the abſorbent veſſels of vegetables which reſembles the lacteals of animal bodies, and imbibes their nutriment from the moiſt earth, is evinced by their growth ſo long as moiſture is applied to their roots, and their quickly withering when it is withdrawn.
Beſides theſe abſorbents in the roots of plants there are others which open their mouths on the external ſurfaces of the bark and leaves, and on the internal ſurfaces of all the cells, and between the bark and the alburnum or ſap-wood; the exiſtence of theſe is ſhewn, becauſe a leaf plucked off and laid with its under ſide on water will not wither ſo ſoon as if left in the dry air,—the ſame if the bark alone of a branch which is ſeparated from a tree be kept moiſt with water,—and laſtly, by moiſtening the alburnum or ſap-wood alone of a branch detached from a tree it will not ſo ſoon wither as if left in the dry air. By the following experiment theſe veſſels were agreeably viſible by a common magnifying glaſs, I placed in the ſummer of 1781 the footſtalks of ſome large fig-leaves about an inch deep in a decoction of madder, (rubia tinctorum,) and others in a decoction of logwood, (haematoxylum campechenſe,) along with ſome ſprigs cut off from a plant of picris, theſe plants were choſen becauſe their blood is white, after ſome hours, and on the next day, on taking out either of theſe and cutting off from its bottom about a quarter of an inch of the ſtalk an internal circle of red points appeared, which were the ends of abſorbent veſſels coloured red with the decoction, while an external ring of arteries was ſeen to bleed out haſtily a milky juice, and at once evinced both the abſorbent and arterial ſyſtem. Theſe abſorbent veſſels have been called by Grew, and Malphigi, and ſome other philoſophers, bronchi, and erroneouſly ſuppoſed to be air-veſſels. It is probable that theſe veſſels, when cut through, may effuſe their fluids, and receive air, their ſides being too ſtiff to collapſe; ſince dry wood emits airbubles in the exhauſted receiver in the ſame manner as moiſt wood.
The ſtructure of theſe vegetable abſorbents conſiſts of a ſpiral line, and not of a veſſel interrupted with valves like the animal lymphatics, ſince on breaking almoſt any tender leaf and drawing out ſome of the fibres which adhere longeſt this ſpiral ſtructure becomes viſible even to the naked eye, and diſtinctly ſo by the uſe of a common lens. See Grew, Plate 51.
In ſuch a ſtructure it is eaſy to conceive how a vermicular or periſtaltic motion of the veſſel beginning at the loweſt part of it, each ſpiral ring ſucceſſively contracting itſelf till it fills up the tube, muſt forcibly puſh forwards its contents, as from the roots of vines in the bleeding ſeaſon; and if this vermicular motion ſhould begin at the upper end of the veſſel it is as eaſy to ſee how it muſt carry its contained fluid in a contrary direction. The retrograde motion of the vegetable abſorbent veſſels is ſhewn by cutting a forked branch from a tree, and immerſing a part of one of the forks in water, which will for many days prevent the other from withering; or it is ſhewn by planting a willow branch with the wrong end upwards. This ſtructure in ſome degree obtains in the eſophagus or throat of cows, who by ſimilar means convey their food firſt downwards [Page 100] and afterward upwards by a retrograde motion of the annular muſcles or cartilages for the purpoſe of a ſecond maſtication of it.
II. The fluids thus drank up by the vegetable abſorbent veſſels from the earth, or from the atmoſphere, or from their own cells and interſtices, are carried to the foot-ſtalk of every leaf, where the abſorbents belonging to each leaf unite into branches, forming ſo many pulmonary arteries, and are thence diſperſed to the extremities of the leaf, as may be ſeen in cutting away ſlice after ſlice the footſtalk of a horſe-cheſnut in September before the leaf falls. There is then a compleat circulation in the leaf, a pulmonary vein receiving the blood from the extremities of each artery on the upper ſide of the leaf, and joining again in the footſtalk of the leaf theſe veins produce ſo many arteries, or aortas, which diſperſe the new blood over the new bark, elongating its veſſels, or producing its ſecretions; but as a reſervoir of blood could not be wanted by a vegetable bud which takes in its nutriment at all times, I imagine there is no venous ſyſtem, no veins properly ſo called, which receive the blood which was to ſpare, and return it into the pulmonary or arterial ſyſtem.
The want of a ſyſtem of veins was countenanced by the following experiment; I cut off ſeveral ſtems of tall ſpurge, (Euphorbia helioſcopia) in autumn, about the centre of the plant, and obſerved tenfold the quantity of milky juice ooze from the upper than from the lower extremity, which could hardly have happened if there had been a venous ſyſtem of veſſels to return the blood from the roots to the leaves.
Thus the vegetable circulation, complete in the lungs, but probably in the other part of the ſyſtem deficient in reſpect to a ſyſtem of returning veins, is carried forwards without a heart, like the circulation through the livers of animals where the blood brought from the inteſtines and meſentery by one vein is diſperſed through the liver by the vena portarum, which aſſumes the office of an artery. See Note XXXVII.
At the ſame time ſo minute are the veſſels in the intertexture of the barks of plants, which belong to each individual bud, that a general circulation may poſſibly exiſt, though we have not yet been able to diſcover the venous part of it.
There is however another part of the circulation of vegetable juices viſible to the naked eye, and that is in the corol or petals of flowers, in which a part of the blood of the plant is expoſed to the influence of the air and light in the ſame manner as in the foliage, as will be mentioned more at large in Notes XXXVII and XXXIX.
Theſe circulations of their reſpective fluids ſeem to be carried on in the veſſels of plants preciſely as in animal bodies by their irritability to the ſtimulus of their adapted fluids, and not by any mechanical or chemical attraction, for their abſorbent veſſels propel the juice upwards, which they drink up from the earth, with great violence; I ſuppoſe with much greater than is exerted by the lacteals of animals, probably owing to the greater minuteneſs of theſe veſſels in vegetables and the greater rigidity of their coats. Dr. Hales in the ſpring ſeaſon cut off a vine near the ground, and by fixing tubes on the remaining ſtump of it, found the ſap to riſe twenty-one feet in the tube by the propulſive [Page 101] power of theſe abſorbents of the roots of it. Veget. Stat. p. 102. Such a power can not be produced by capillary attraction, as that could only raiſe a fluid nearly to the upper edge of the attracting cylinder, but not enable it to flow over that edge, and much leſs to riſe 21 feet above it. What then can this power be owing to? Doubtleſs to the living activity of the abſorbent veſſels, and to their increaſed vivacity from the influence of the warmth of the ſpring ſucceeding the winter's cold, and their thence greater ſuſceptibility to irritation from the juices which they abſorb, reſembling in all circumſtances the action of the living veſſels of animals.
While ſpread in air the leaves reſpiring play.CANTO IV. l. 421.
I. THERE have been various opinions concerning the uſe of the leaves of plants in the vegetable oeconomy. Some have contended that they are perſpiratory organs; this does not ſeem probable from an experiment of Dr. Hales, Veg. Stat. p. 30. He found by cutting off branches of trees with apples on them, and taking off the leaves, that an apple exhaled about as much as two leaves, the ſurfaces of which were nearly equal to the apple; whence it would appear that apples have as good a claim to be termed perſpiratory organs as leaves. Others have believed them excretory organs of excrementious juices; but as the vapour exhaled from vegetables has no taſte, this idea is no more probable than the other; add to this that in moiſt weather, they do not appear to perſpire or exhale at all.
The internal ſurface of the lungs or air-veſſels in men, are ſaid to be equal to the external ſurface of the whole body, or about fifteen ſquare feet; on this ſurface the blood is expoſed to the influence of the reſpired air through the medium however of a thin pellicle; by this expoſure to the air it has its colour changed from deep red to bright ſcarlet, and acquires ſomething ſo neceſſary to the exiſtence of life, that we can live ſcarcely a minute without this wonderful proceſs.
1. The great ſurface of the leaves compared to that of the trunk and branches of trees is ſuch, that it would ſeem to be an organ well adapted for the purpoſe of expoſing the vegetable juices to the influence of the air; this however we ſhall ſee afterwards is probably performed only by their upper ſurfaces, yet even in this caſe the ſurface of the leaves in general bear a greater proportion to the ſurface of the tree, than the lungs of animals to their external ſurfaces.
[Page 102] 2. In the lungs of animal, the blood after having been expoſed to the air in the extremities of pulmonary artery, is changed in colour from deep red to bright ſcarlet, and certainly in ſome of its eſſential properties; it is then collected by the pulmonary vein and returned to the heart. To ſhew a ſimilarity of circumſtance in the leaves of plants the following experiment was made, June 24, 1781: A ſtalk with leaves and ſeed-veſſels of large ſpurge (Euphorbia helioſcopia) had been ſeveral days placed in a decoction of madder (Rubia tinctorum) ſo that the lower part of the ſtem, and two of the undermoſt leaves were immerſed in it. After having waſhed the immerſed leaves in clear water, I could readily diſcern the colour of the madder paſſing along the middle rib of each leaf. This red artery was beautifully viſible both on the under and upper ſurface of the leaf; but on the upper ſide many red branches were ſeen going from it to the extremities of the leaf, which on the other ſide were not viſible except by looking through it againſt the light. On this under ſide a ſyſtem of branching veſſels carrying a pale milky fluid were ſeen coming from the extremities of the leaf, and covering the whole underſide of it, and joining into two large veins, one on each ſide of the red artery in the middle rib of the leaf, and along with it deſcending to the footſtalk or petiole. On ſlitting one of theſe leaves with ſciſſars, and having a common magnifying lens ready, the milky blood was ſeen oozing out of the returning veins on each ſide of the red artery in the middle rib, but none of the red fluid from the artery.
All theſe appearances were more eaſily ſeen in a leaf of Picris treated in the ſame manner; for in this milky plant the ſtems and middle rib of the leaves are ſometimes naturally coloured reddiſh, and hence the colour of the madder ſeemed to paſs further into the ramifications of their leaf-arteries, and was there beautifully viſible with the returning branches of milky veins on each ſide.
3. From theſe experiments the upper ſurface of the leaf appeared to be the immediate organ of reſpiration, becauſe the coloured fluid was carried to the extremities of the leaf by veſſels moſt conſpicuous on the upper ſurface, and there changed into a milky fluid, which is the blood of the plant, and then returned by concomitant veins on the under ſurface, which were ſeen to ooze when divided with ſciſſars, and which in Picris, particularly render the under ſurface of the leaves greatly whiter than the upper one.
4. As the upper ſurface of leaves conſtitutes the organ of reſpiration, on which the ſap is expoſed in the terminations of arteries beneath a thin pellicle to the action of the atmoſphere, theſe ſurfaces in many plants ſtrongly repel moiſture, as cabbage-leaves, whence the particles of rain lying over their ſurfaces without touching them, as obſerved by Mr. Melville (Eſſays Literary and Philoſop. Edinburgh) have the appearance of globules of quickſilver. And hence leaves laid with the upper ſurfaces on water, wither as ſoon as in the dry air, but continue green many days, if placed with the under ſurfaces on water, as appears in the experiments of Mons. Bonnet (Uſage des Fevilles.) Hence ſome aquatic plants, as the Water-lily (Nymphoea) have the lower ſides of their leaves floating on the water, while the upper ſurfaces remain dry in the air.
5. As thoſe inſects, which have many ſpiracula, or breathing apertures, as waſps and flies, are immediately ſuffocated by pouring oil upon them, I carefully covered with [Page 103] oil the ſurfaces of ſeveral leaves of Phlomis, of Portugal Laurel, and Balſams, and though it would not regularly adhere, I found them all die in a day or two.
Of aquatic leaves, ſee Note on Trapa and on Fucus, in Vol. II. to which muſt be added that many leaves are furniſhed with muſcles about their footſtalks, to turn their upper ſurfaces to the air or light, as Mimoſa and Hedyſarum gyrans. From all theſe analogies I think there can be no doubt but that leaves of trees are their lungs, giving out a phlogiſtic material to the atmoſphere, and abſorbing oxygene or vital air.
6. The great uſe of light to vegetation would appear from this theory to be by diſengaging vital air from the water which they perſpire, and thence to facilitate its union with their blood expoſed beneath the thin ſurface of their leaves; ſince when pure air is thus applied, it is probable, that it can be more readily abſorbed. Hence in the curious experiments of Dr. Prieſtley and Mr. Ingenhouze, ſome plants purified air leſs than others, that is, they perſpired leſs in the ſunſhine; and Mr. Scheele found that by putting peas into water, which about half-covered them, that they converted the vital air into fixed air, or carbonic acid gas, in the ſame manner as in animal reſpiration. See Note XXXIV.
7. The circulation in the lungs or leaves of plants is very ſimilar to that of fiſh. In fiſh the blood after having paſſed through their gills does not return to the heart as from the lungs of air-breathing animals, but the pulmonary vein taking the ſtructure of an artery after having received the blood from the gills, which there gains a more florrid colour, diſtributes it to the other parts of their bodies. The ſame ſtructure occurs in the livers of fiſh, whence we ſee in thoſe animals two circulations independent of the power of the heart, viz. that beginning at the termination of the veins of the gills, and branching through the muſcles; and that which paſſes through the liver; both which are carried on by the action of thoſe reſpective arteries and veins. Monro's Phyſiology of Fiſh, p. 19.
The courſe of the fluids in the roots, leaves, and buds of vegetables ſeems to be performed in a manner ſimilar to both theſe. Firſt the abſorbent veſſels of the roots and ſurfaces unite at the footſtalk of the leaf; and then, like the Vena Portarum, an artery commences without the intervention of a heart, and ſpreads the ſap in its numerous ramifications on the upper ſurface of the leaf; here it changes its colour and properties, and becomes vegetable blood; and is again collected by a pulmonary vein on the under ſurface of the leaf. This vein, like that which receives the blood from the gills of fiſh, aſſumes the office and name of an artery, and branching again diſperſes the blood upward to the bud from the footſtalk of the leaf, and downward to the roots; where it is all expended in the various ſecretions, the nouriſhment and growth of the plant, as faſt as it is prepared.
II. The organ of reſpiration already ſpoken of belongs particularly to the ſhoots or buds, but there is another pulmonary ſyſtem, perhaps totally independent of the green foliage, which belongs to the fructification only, I mean the corol or petals. In this there is an artery belonging to each petal, which conveys the vegetable blood to its extremities, expoſing it to the light and air under a delicate membrane covering the internal ſurface of the petal, where it often changes its colour, as is beautifully ſeen in ſome party-coloured [Page 104] poppies; though it is probable ſome of the irideſcent colours of flowers may be owing to the different degrees of tenuity of the exterior membrane of the leaf refracting the light like ſoap-bubbles, the vegetable blood is then returned by correſpondent vegetable veins, exactly as in the green foliage; for the purpoſes of the important ſecretions of honey, wax, the finer eſſential oil, and the prolific duſt of the anthers.
1. The vaſcular ſtructure of the corol as above deſcribed, and which is viſible to the naked eye, and its expoſing the vegetable juices to the air and light during the day, evinces that it is a pulmonary organ.
2. As the glands which produce the prolific duſt of the anthers, the honey, wax, and frequently ſome odoriferous eſſential oil, are generally attached to the corol, and always fall off and periſh with it, it is evident that the blood is elaborated or oxygenated in this pulmonary ſyſtem for the purpoſe of theſe important ſecretions.
3. Many flowers, as the Colchicum, and Hamamelis ariſe naked in autumn, no green leaves appearing till the enſuing ſpring; and many others put forth their flowers and complete their impregnation early in the ſpring before the green foliage appears, as Mezereon, cherries, pears, which ſhews that theſe corols are the lungs belonging to the fructification.
4. This organ does not ſeem to have been neceſſary for the defence of the ſtamens and piſtils, ſince the calyx of many flowers, as Tragopogon, performs this office; and in many flowers theſe petals themſelves are ſo tender as to require being ſhut up in the calyx during the night, for what other uſe then can ſuch an apparatus of veſſels be deſigned?
5. In the Helleborus-niger, Chriſtmas-roſe, after the ſeeds are grown to a certain ſize, the nectaries and ſtamens drop off, and the beautiful large white petals change their colour to a deep green, and gradually thus become as calyx incloſing and defending the ripening ſeeds, hence it would ſeem that the white veſſels of the corol ſerved the office of expoſing the blood to the action of the air, for the purpoſes of ſeparating or producing the honey, wax, and prolific duſt, and when theſe were no longer wanted, that theſe veſſels coaleſced like the placental veſſels of animals after their birth, and thus ceaſed to perform that office and loſt at the ſame time their white colour. Why ſhould they looſe their white colour, unleſs they at the ſame time loſt ſome other property beſides that of defending the ſeed-veſſel, which they ſtill continue to defend?
6. From theſe obſervations I am led to doubt whether green leaves be abſolutely neceſſary to the progreſs of the fruit-bud after the laſt year's leaves are fallen off. The green leaves ſerve as lungs to the ſhoots and foſter the new buds in their boſoms, whether theſe buds be leaf-buds or fruit-buds; but in the early ſpring the fruit-buds expand their corols, which are their lungs, and ſeem no longer to require green leaves; hence the vine bears fruit at one joint without leaves, and puts out a leaf-bud at another joint without fruit. And I ſuppoſe the green leaves which riſe out of the earth in the ſpring from the Colchicum are for the purpoſe of producing the new bulb, and its placenta, and not for the giving maturity to the ſeed. When currant or gooſberry trees loſe their leaves by the depredation of inſects the fruit continues to be formed, though leſs ſweet and leſs in ſize.
[Page 105] 7. From theſe facts it appears that the flower-bud after the corol falls off, (which is its lungs,) and the ſtamens and nectary along with it, becomes ſimply an uterus for the purpoſe of ſupplying the growing embryon with nouriſhment, together with a ſyſtem of abſorbent veſſels which bring the juices of the earth to the footſtalk of the fruit, and which there changes into an artery for the purpoſe of diſtributing the ſap for the ſecretion of the ſaccharine or farinaceous or aceſcent materials for the uſe of the embryon. At the ſame time as all the veſſels of the different buds of trees inoſculate or communicate with each other, the fruit becomes ſweeter and larger when the green leaves continue on the tree, but the mature flowers themſelves, (the ſucceeding fruit not conſidered) perhaps ſuffer little injury from the green leaves being taken off, as ſome floriſts have obſerved.
8. That the veſſels of different vegetable buds inoſculate in various parts of their circulation is rendered probable by the increaſed growth of one bud, when others in its vicinity are cut away; as it thus ſeems to receive the nouriſhment which was before divided amongſt many.
Love out their hour and leave their lives in air.CANTO IV. l. 456.
FROM the accurate experiments and obſervations of Spallanzani it appears that in the Spartium Junceum, ruſh-broom, the very minute ſeeds were diſcerned in the pod at leaſt twenty days before the flower is in full bloom, that is twenty days before fecundation. At this time alſo the powder of the anthers was viſible, but glued faſt to their ſummits. The ſeeds however at this time, and for ten days after the bloſſom had fallen off, appeared to conſiſt of a gelatinous ſubſtance. On the eleventh day after the falling of the bloſſom the ſeeds became heart-ſhape, with the baſis attached by an appendage to the pod, and a white point at the apex; this white point was on preſſure found to be a cavity including a drop of liquor.
On the 25th day the cavity which at firſt appeared at the apex was much enlarged and ſtill full of liquor, it alſo contained a very ſmall ſemi-tranſparent body, of a yellowiſh colour, gelatinous, and fixed by its two oppoſite ends to the ſides of the cavity.
In a month the ſeed was much enlarged and its ſhape changed from a heart to a kidney, the little body contained in the cavity was increaſed in bulk and was leſs tranſparent, and gelatinous, but there yet appeared no organization.
[Page 106] On the 40th day the cavity now grown larger was quite filled with the body, which was covered with a thin membrane; after this membrane was removed the body appeared of a bright green, and was eaſily divided by the point of a needle into two portions, which manifeſtly formed the two lobes, and within theſe attached to the lower part the exceedingly ſmall plantule was eaſily perceived.
The foregoing obſervations evince, 1. That the ſeeds exiſt in the ovarium many days before fecundation. 2. That they remain for ſome time ſolid, and then a cavity containing a liquid is formed in them. 3. That after fecundation a body begins to appear within the cavity fixed by two points to the ſides, which in proceſs of time proves to be two lobes containing a plantule. 4. That the ripe ſeed conſiſts of two lobes adhering to a plantule, and ſurrounded by a thin membrane which is itſelf covered with a huſk or cuticle. Spalanzani's Diſſertations, Vol. II. p. 253.
The analogy between ſeeds and eggs has long been obſerved, and is confirmed by the mode of their production. The egg is known to be formed within the hen long before its impregnation; C. F. Wolf aſſerts that the yolk or the egg is nouriſhed by the veſſels of the mother, and that it has from thoſe its arterial and venous branches, but that after impregnation theſe veſſels gradually become impervious and obliterated, and that new ones are produced from the fetus and diſperſed into the yolk. Haller's Phyſiolog. Tom. VIII. p. 94. The young ſeed after fecundation, I ſuppoſe, is nouriſhed in a ſimilar manner from the gelatinous liquor, which is previouſly depoſited for that purpoſe; the uterus of the plant producing or ſecreting it into a reſervoir or amnios in which the embryon is lodged, and that the young embryon is furniſhed with veſſels to abſorb a part of it, as in the very early embryon in the animal uterus.
The ſpawn of frogs and of fiſh is delivered from the female before its impregnation. M. Bonnet ſays that the male ſalamander darts his ſemen into the water, where it forms a little whitiſh cloud which is afterwards received by the ſwoln anus of the female, and ſhe is fecundated.—He adds that marine plants approach near to theſe animals, as the male does not project a fine powder but a liquor which in like manner forms a little cloud in the water.—And further adds, who knows but the powder of the ſtamina of certain plants may not make ſome impreſſion on certain germs belonging to the animal kingdom! Letter XLIII. to Spalanzani, Oevres Philoſ.
Spalanzani found that the ſeminal fluid of frogs and dogs even when diluted with much water retained its prolific quality. Whether this quality be ſimply a ſtimulus exciting the egg into animal action, which may be called a vivifying principle, or whether part of it be actually conjoined with the egg is not yet determined, though the latter ſeems more probable from the frequent reſemblance of the fetus to the male parent. A conjunction however of both the male and female influence ſeems neceſſary for the purpoſe of reproduction throughout all organized nature, as well in hermaphrodite inſects, microſcopic animals, and polypi, and exiſts as well in the formation of the buds of vegetables as in the production of their ſeeds, which is ingeniouſly conceived and explained by Linneus. After having compared the flower to the larva of a butterfly, [Page 107] conſiſting of petals inſtead of wings, calyxes inſtead of wing-ſheaths, with the organs of reproduction, and having ſhewn the uſe of the farina in fecundating the egg or ſeed, he proceeds to explain the production of the bud. The calyx of a flower, he ſays, is an expanſion of the outer bark, the petals proceed from the inner bark or rind, the ſtamens from the alburnum or woody circle, and the ſtyle from the pith. In the production and impregnation of the ſeed a commixture of the ſecretions of the ſtamens and ſtyle are neceſſary; and for the production of a bud he thinks the medulla or pith burſts its integuments and mixes with the woody part or alburnum, and theſe forcing their paſſage through the rind and bark conſtitute the bud or viviparous progeny of the vegetable. Syſtem of Vegetables tranſlated from Linneus, p. 8.
It has been ſuppoſed that the embryon vegetable after fecundation, by its living activity or ſtimulus exerted on the veſſels of the parent plant, may produce the fruit or ſeed-lobes, as the animal fetus produces its placenta, and as vegetable buds may be ſuppoſed to produce their umbilical veſſels or roots down the bark of the tree. This in reſpect to the production of the fruit ſurrounding the ſeeds of trees has been aſſimilated to the gall-nuts on oak-leaves, and to the bedeguar on briars, but there is a powerful objection to this doctrine, viz. that the fruit of figs, all which are female in this country, grow nearly as large without fecundation, and therefore the embryon has in them no ſelf-living principle.
Seeks, where fine pores their dulcet balm diſtil.CANTO IV. l. 503.
THE glands of vegetables which ſeparate from their blood the mucilage, ſtarch, or ſugar for the placentation or ſupport of their ſeeds, bulbs, and buds; or thoſe which depoſit their bitter, acrid, or narcotic juices for their defence from depredations of infects or larger animals; or thoſe which ſecrete reſins or wax for their protection from moiſture or froſts, conſiſt of veſſels too fine for the injection or abſorption of coloured fluids, and have not therefore yet been exhibited to the inſpection even of our glaſſes, and can therefore only be known by their effects, but one of the moſt curious and important of all vegetable ſecretions, that of honey, is apparent to our naked eyes, though before the diſcoveries of Linneus the nectary or honey-gland had not even acquired a name.
[Page 108] The odoriferous eſſential oils of ſeveral flowers ſeem to have been deſigned for their defence againſt the depredations of inſects, while their beautiful colours were a neceſſary conſequence of the ſize of the particles of their blood, or of the tenuity of the exterior membrane of the petal. The uſe of the prolific duſt is now well aſcertained, the wax which covers the anthers prevents this duſt from receiving moiſture, which would make it burſt prematurely and thence prevent its application to the ſtigma, as ſometimes happens in moiſt years and is the cauſe of deficient fecundation both of our fields and orchards.
The univerſality of the production of honey in the vegetable world, and the very complicated apparatus which nature has conſtructed in many flowers, as well as the acrid or deleterious juices ſhe has furniſhed thoſe flowers with (as in the Aconite) to protect this honey from rain and from the depredations of inſects, ſeem to imply that this fluid is of very great importance in the vegetable economy; and alſo that it was neceſſary to expoſe it to the open air previous to its reabſorption into the vegetable veſſels.
In the animal ſyſtem the lachrymal gland ſeparates its fluid into the open air for the purpoſe of moiſtening the eye, of this fluid the part which does not exhale is abſorbed by the puncta lachrymalia and carried into the noſtrils; but as this is not a nutritive fluid the analogy goes no further than its ſecretion into the open air and its reabſorption into the ſyſtem; every other ſecreted fluid in the animal body is in part abſorbed again into the ſyſtem, even thoſe which are eſteemed excrementitious, as the urine and perſpirable matter, of which the latter is ſecreted, like the honey, into the external air. That the honey is a nutritious fluid, perhaps the moſt ſo of any vegetable production, appears from its great ſimilarity to ſugar, and from its affording ſuſtenance to ſuch numbers of inſects, which live upon it ſolely during ſummer, and lay it up for their winter proviſion. Theſe proofs of its nutritive nature evince the neceſſity of its reabſorption into the vegetable ſyſtem for ſome uſeful purpoſe.
This purpoſe however has as yet eſcaped the reſearches of philoſophical botaniſts. M. Pontedera believes it deſigned to lubricate the vegetable uterus, and compares the horn-like nectaries of ſome flowers to the appendicle of the caecum inteſtinum of animals. Antholog. p. 49.) Others have ſuppoſed that the honey, when reabſorbed, might ſerve the purpoſe of the liquor amnii, or white of the egg, as a nutriment for the young embryon or fecundated ſeed in its early ſtate of exiſtence. But as the nectary is found equally general in male flowers as in female ones; and as the young embryon or ſeed grows before the petals and nectary are expanded, and after they fall off; and, thirdly, as the nectary ſo ſoon falls off after the fecundation of the piſtillum; theſe ſeem to be inſurmountable objections to both the above-mentioned opinions.
In this ſtate of uncertainty conjectures may be of uſe ſo far as they lead to further experiment and inveſtigation. In many tribes of inſects, as the ſilk-worm, and perhaps in all the moths and butterflies, the male and female parents die as ſoon as the eggs are [Page 109] impregnated and excluded; the eggs remaining to be perfected and hatched at ſome future time. The ſame thing happens in regard to the male and female parts of flowers; the anthers and filaments, which conſtitute the male parts of the flower, and the ſtigma and ſtyle, which conſtitute the female part of the flower, fall off and die as ſoon as the ſeeds are impregnated, and along with theſe the petals and nectary. Now the moths and butterflies above-mentioned, as ſoon as they acquire the paſſion and the apparatus for the reproduction of their ſpecies, looſe the power of feeding upon leaves as they did before, and become nouriſhed by what?—by honey alone.
Hence we acquire a ſtrong analogy for the uſe of the nectary or ſecretion of honey in the vegetable economy, which is, that the male parts of flowers, and the female parts, as ſoon as they leave their fetus-ſtate, expanding their petals, (which conſtitute their lungs,) become ſenſible to the paſſion, and gain the apparatus for the reproduction of their ſpecies, and are fed and nouriſhed with honey like the inſects above deſcribed; and that hence the nectary begins its office of producing honey, and dies or ceaſes to produce honey at the ſame time with the birth and death of the ſtamens and the piſtils; which, whether exiſting in the ſame or in different flowers, are ſeparate and diſtinct animated beings.
Previous to this time the anthers with their filaments, and the ſtigmas with their ſtyles, are in their fetus-ſtate ſuſtained by their placental veſſels, like the unexpanded leaf-bud; with the ſeeds exiſting in the vegetable womb yet unimpregnated, and the duſt yet unripe in the cells of the anthers. After this period they expand their petals, which have been ſhewn above to conſtitute the lungs of the flower; the placental veſſels, which before nouriſhed the anthers and the ſtigmas, coaleſce or ceaſe to nouriſh them; and they now acquire blood more oxygenated by the air, obtain the paſſion and power of reproduction, are ſenſible to heat, and cold, and moiſture, and to mechanic ſtimulus, and become in reality inſects fed with honey, ſimilar in every reſpect except their being attached to the tree on which they were produced.
Some experiments I have made this ſummer by cutting out the nectaries of ſeveral flowers of the aconites before the petals were open, or had become much coloured, ſome of theſe flowers near the ſummit of the plants produced no ſeeds, others lower down produced ſeeds; but they were not ſufficiently guarded from the farina of the flowers in their vicinity; nor have I had opportunity to try if theſe ſeeds would vegetate.
I am acquainted with a philoſopher, who contemplating this ſubject thinks it not impoſſible, that the firſt inſects were the anthers or ſtigmas of flowers; which had-by ſome means looſed themſelves from their parent plant, like the male flowers of Valliſneria; and that many other inſects have gradually in long proceſs of time been formed from theſe; ſome acquiring wings, others fins, and others claws, from their ceaſeleſs efforts to procure their food, or to ſecure themſelves from injury. He contends, that none of theſe changes are more incomprehenſible than the tranſformation of tadpoles into frogs, and caterpillars into butterflies.
There are parts of animal bodies, which do not require oxygenated blood for the purpoſe of their ſecretions, as the liver; which for the production of bile takes its blood [Page 110] from the meſenteric veins, after it muſt have loſt the whole or a great part of its oxygenation, which it had acquired in its paſſage through the lungs. In like manner the pericarpium, or womb of the flower, continues to ſecrete its proper juices for the preſent nouriſhment of the newly animated embryon-ſeed; and the ſaccharine, aceſcent, or ſtarchy matter of the fruit or ſeed-lobes for its future growth; in the ſame manner as theſe things went on before fecundation; that is, without any circulation of juices in the petals, or production of honey in the nectary; theſe having periſhed and fallen off with the male and female apparatus for impregnation.
It is probable that the depredations of inſects on this nutritious fluid muſt be injurious to the products of vegetation, and would be much more ſo, but that the plants have either acquired means to defend their honey in part, or have learned to make more than is abſolutely neceſſary for their own economy. In the ſame manner the honey-dew on trees is very injurions to them; in which diſeaſe the nutritive fluid, the vegetable-ſap-juice, ſeems to be exſuded by a retrograde motion of the cutaneous lymphatics, as in the ſweating ſickneſs of the laſt century. To prevent the depredation of inſects on honey a wealthy man in Italy is ſaid to have poiſoned his neighbour's bees perhaps by mixing arſnic with honey, againſt which there is a moſt flowery declamation in Quintilian. No. XIII. As the uſe of the wax is to preſerve the duſt of the anthers from moiſture, which would prematurely burſt them, the bees which collect this for the conſtruction of the combs or cells, muſt on this account alſo injure the vegetation of a country where they too much abound.
It is not eaſy to conjecture why it was neceſſary that this ſecretion of honey ſhould be expoſed to the open air in the nectary or honey-cup, for which purpoſe of great an apparatus for its defence from inſects and from ſhowers became neceſſary. This difficulty increaſes when we recollect that the ſugar in the joints of graſs, in the ſugar-cane, and in the roots of beets, and in ripe fruits is produced without the expoſure to the air. On ſuppoſition of its ſerving for nutriment to the anthers and ſtigmas it may thus acquire greater oxygenation for the purpoſe of producing greater powers of ſenſibility, according to a doctrine lately advanced by a French philoſopher, who has endeavoured to ſhew that the oxygene, or baſe of vital air, is the conſtituent principle of our power of ſenſibility.
From this proviſion of honey for the male and female parts of flowers, and from the proviſion of ſugar, ſtarch, oil, and mucilage, in the fruits, ſeed-cotyledons, roots, and buds of plants laid up for the nutriment of the expanding fetus, not only a very numerous claſs of inſects, but a great part of the larger animals procure their food; and thus enjoy life and pleaſure without producing pain to others, for theſe ſeeds or eggs with the nutriment laid up in them are not yet endued with ſenſitive life.
The ſecretions from various vegetable glands hardened in the air produce gums, reſins, and various kinds of ſaccharine, ſaponaceous, and wax-like ſubſtances, as the gum of cherry or plumb-trees, gum tragacanth from the aſtragalus tragacantha, camphor from the laurus camphora, elemi from amyris elemifera, aneme from hymenoea courbaril, turpentine from piſtacia terebinthus, balſam of Mecca from the buds of amyris opobalſamum, [Page 111] branches of which are placed in the temples of the Eaſt on account of their fragrance, the wood is called xylobalſamum, and the fruit carpobalſamum; aloe from a plant of the ſame name; myrrh from a plant not yet deſcribed; the remarkably elaſtic reſin is brought into Europe principally in the form of flaſks, which look like black leather, and are wonderfully elaſtic, and not penetrable by water, rectified ether diſſolves it; its flexibility is encreaſed by warmth and deſtroyed by cold; the tree which yields this juice is the jatropha elaſtica, it grows in Guaiana and the neighbouring tracts of America; its juice is ſaid to reſemble wax in becoming ſoft by heat, but that it acquires no elaſticity till that property is communicated to it by a ſecret art, after which it is poured into moulds and well dried and can no longer be rendered fluid by heat. Mr. de la Borde phyſician at Cayenne has given this account. Manna is obtained at Naples from the fraxinus ornus, or manna-aſh, it partly iſſues ſpontaneouſly, which is preferred, and partly exſudes from wounds made purpoſely in the month of Auguſt, many other plants yield manna more ſparingly; ſugar is properly made from the ſaccharum officinale, or ſugar-cane, but is found in the roots of beet and many other plants; American wax is obtained from the myrica cerifera, candle-berry myrtle, the berries are boiled in water and a green wax ſeparates, with luke warm water the wax is yellow: the ſeed of croton ſebiferum are lodged in tallow; there are many other vegetable exſudations uſed in the various arts of dyeing, varniſhing, tanning, lacquering, and which ſupply the ſhop of the druggiſt with medicines and with poiſons.
There is another analogy, which would ſeem to aſſociate plants with animals, and which perhaps belongs to this Note on Glandulation, I mean the ſimilarity of their digeſtive powers. In the roots of growing vegetables, as in the proceſs of making malt, the farinaceous part of the ſeed is converted into ſugar by the vegetable power of digeſtion in the ſame manner as the farinaceous matter of ſeeds are converted into ſweet chyle by the animal digeſtion. The ſap-juice which riſes in the vernal months from the roots of trees through the alburnum or ſap-wood, owes its ſweetneſs I ſuppoſe to a ſimilar digeſtive power of the abſorbent ſyſtem of the young buds. This exiſts in many vegetables in great abundance as in vines, ſycamore, birch, and moſt abundantly in the palm-tree, (Iſert's Voyage to Guinea,) and ſeems to be a ſimilar fluid in all plants, as chyle is ſimilar in all animals.
Hence as the digeſted food of vegetables conſiſts principally of ſugar, and from that is produced again their mucilage, ſtarch, and oil, and ſince animals are ſuſtained by theſe vegetable productions, it would ſeem that the ſugar-making proceſs carried on in vegetable veſſels was the great ſource of life to all organized beings. And that if our improved chemiſtry ſhould ever diſcover the art of making ſugar from foſſile or aerial matter without the aſſiſtance of vegetation, food for animals would then become as plentiful as water, and mankind might live upon the earth as thick as blades of graſs, with no reſtraint to their numbers but the want of local room.
It would ſeem that roots fixed in the earth, and leaves innumerable waving in the air were neceſſary forthe decompoſition of water, and the converſion of it into ſaccharine [Page 112] matter, which would have been not only cumberous but totally incompatible with the locomotion of animal bodies. For how could a man or quadruped have carried on his head or back a foreſt of leaves, or have had long branching lacteal or abſorbent veſſels terminating in the earth? Animals therefore ſubſiſt on vegetables; that is, they take the matter ſo far prepared, and have organs to prepare it further for the purpoſes of higher animation, and greater ſenſibility. In the ſame manner the apparatus of green leaves and long roots were found inconvenient for the more animated and ſenſitive parts of vegetable-flowers, I mean the anthers and ſtigmas, which are therefore ſeparate beings, endued with the paſſion and power of reproduction, with lungs of their own, and fed with honey, a food ready prepared by the long roots and green leaves of the plant, and preſented to their abſorbent mouths.
From this outline a philoſopher may catch a glimpſe of the general economy of nature; and like the mariner caſt upon an unknown ſhore, who rejoiced when he ſaw the print of a human foot upon the ſand, he may cry out with rapture, "A GOD DWELLS HERE."
FROM this account of the production of coals from moraſſes it would appear, that coal-beds are not to be expected beneath maſſes of lime-ſtone. Nevertheleſs I have been lately informed by my friend Mr. Michell of Thornhill, who I hope will ſoon favour the public with his geological inveſtigations, that the beds of chalk are the uppermoſt of all the limeſtones; and that they reſt on the granulated limeſtone, called ketton-ſtone; which I ſuppoſe is ſimilar to that which covers the whole country from Leadenham to Sleaford, and from Sleaford to Lincoln; and that, thirdly, coal-delphs are frequently found beneath theſe two uppermoſt beds of limeſtone.
Now as the beds of chalk and of granulated limeſtone may have been formed by alluviation, on or beneath the ſhores of the ſea, or in vallies of the land; it would ſeem, that ſome coal countries, which in the great commotions of the earth had been ſunk beneath the water, were thus covered with alluvial limeſtone, as well as others with alluvial baſaltes, or common gravel-beds. Very extenſive plains which now conſiſt of alluvial materials, were in the early times covered with water; which has ſince diminiſhed, as the ſolid parts of the earth have increaſed. For the ſolid parts of the earth conſiſting chiefly of animal and vegetable recrements muſt have originally been formed or produced from the water by animal and vegetable proceſſes; and as the ſolid parts of the earth may be ſuppoſed to be thrice as heavy as water, it follows that thrice the quantity of water muſt have vaniſhed compared with the quantity of earth thus produced. This may account for many immenſe beds of alluvial materials, as gravel, rounded ſand, granulated limeſtone, and chalk, covering ſuch extenſive plains as Lincoln-heath, having become dry without the ſuppoſition of their having been again elevated from the ocean. At the ſame time we acquire the knowledge of one of the uſes or final cauſes of the organized world, not indeed very flattering to our vanity, that it converts water into earth, forming iſlands and continents by its recrements or exuviae.
Expiring groans, p. 98. l. 451. Mr. Savery or Mr. Volney in their Travels through Egypt has given a curious deſcription of one of the pyramids, with the operoſe method of cloſing them, and immuring the body, (as they ſuppoſed) for ſix thouſand years. And has endeavoured from thence to ſhew, that, when a monarch died, ſeveral of his favourite courtiers were incloſed alive with the mummy in theſe great maſſes of ſtone-work; and had food and water conveyed to them, as long as they lived, proper apertures being left for this purpoſe, and for the admiſſion of air, and for the excluſion of any thing offenſive.
Unfolds his larva-form. p. 197. l. 458. The flower burſts forth from its larva, the herb, naked and perfect like a butterfly from its chryſolis; winged with its corol; wing-ſheathed by its calyx; conſiſting alone of the organs of reproduction. The males, or ſtamens, have their anthers replete with a prolific powder containing the vivifying fovilla: in the females, or piſtils, exiſts the ovary, terminated by the tubular ſtigma. When the anthers burſt and ſhed their bags of duſt, the male fovilla is received by the prolific lymph of the ſtigma, and produces the ſeed or egg, which is nouriſhed in the ovary. Syſtem of Vegetables tranſlated from Linneus by the Lichfield Society, p. 10.
Wound them ye Sylphs! p. 198. 1. 463. It is cuſtomary to debark oak-trees in the ſpring, which are intended to be felled in the enſuing autumn; becauſe the bark comes off eaſier at this ſeaſon, and the ſap-wood, or alburnum, is believed to become harder and more durable, if the tree remains till the end of ſummer. The trees thus ſtripped of their bark put forth ſhoots as uſual with acorns on the 6th 7th and 8th joint, like vines; but in the branches I examined, the joints of the debarked trees were much ſhorter than thoſe of other oak-trees; the acorns were more numerous; and no new buds were produced above the joints which bore acorns. From hence it appears that the branches of debarked oak-trees produce fewer leaf-buds, and more flower-buds, which laſt circumſtance I ſuppoſe muſt depend on their being ſooner or later debarked in the vernal months. And, ſecondly, that the new buds of debarked oak-trees continue to obtain moiſture from the alburnum after the ſeaſon of the aſcent of ſap in other vegetables ceaſes; which in this unnatural ſtate of the debarked tree may act as capillary tubes, like the alburnum of the ſmall debarked cylinder of a pear-tree abovementioned; or may continue to act as placental veſſels, as happens to the animal embryon in caſes of ſuperfetation; when the fetus continues a month or two in the womb beyond its uſual time, of which ſome inſtances have been recorded, the placenta continues to ſupply perhaps the double office both of nutrition and of reſpiration.
[Page 115] With new prolific power. p. 199. l. 467. About Midſummer the new buds are formed, but it is believed by ſome of the Linnean ſchool, that theſe buds may in their early ſtate be either converted into flower-buds or leaf-buds according to the vigour of the vegetating branch. Thus if the upper part of a branch be cut away, the buds near the extremity of the remaining ſtem, having a greater proportional ſupply of nutriment, or poſſeſſing a greater facility of ſhooting their roots, or abſorbent veſſels, down the bark, will become leaf-buds, which might otherwiſe have been flower-buds. And the contrary as explained in note on l. 463. of this Canto.
I conceive the medulla of a plant to conſiſt of a bundle of nervous fibres, and that the propelling vital power ſeparates their uppermoſt extremities. Theſe, diverging, penetrate the bark, which is now gelatinous, and become multiplied in the new gem, or leaf-bud. The aſcending veſſels of the bark being thus divided by the nervous fibres, which perforate it, and the aſcent of its fluids being thus impeded, the bark is extended into a leaf. But the flower is produced, when the protruſion of the medulla is greater than the retention of the including cortical part; whence the ſubſtance of the bark is expanded in the calyx; that of the rind, (or interior bark,) in the corol; that of the wood in the ſtamens, that of the medulla in the piſtil. Vegetation thus terminates in the production of new life, the ultimate medullary and cortical fibres being collected in the ſeeds.Linnei Syſtema Veget. p. 6. edit, 14.
Diana's trees, p. 206. l. 552. The chemiſts and aſtronomers from the earlieſt antiquity have uſed the ſame characters to repreſent the metals and the planets, which were moſt probably outlines or abſtracts of the original hieroglyphic figures of Egypt. Theſe afterwards acquired niches in their temples, and repreſented Gods as well as metals and planets; whence ſilver is called Diana, or the moon, in the books of alchemy.
The proceſs for making Diana's ſilver tree is thus deſcribed by Lemeri. Diſſolve one ounce of pure ſilver in acid of nitre very pure and moderately ſtrong; mix this ſolution with about twenty ounces of diſtilled water; add to this two ounces of mercury, and let it remain at reſt. In about four days there will form upon the mercury a tree of ſilver with branches imitating vegetation.
1. As the mercury has a greater affinity than ſilver with the nitrous acid, the ſilver becomes precipitated; and, being deprived of the nitrous oxygene by the mercury, ſinks down in its metallic form and luſtre. 2. The attraction between ſilver and mercury, which cauſes them readily to amalgamate together, occaſions the precipitated ſilver to adhere to the ſurface of the mercury in preference to any other part of the veſſel. 3. The attraction of the particles of the precipitated ſilver to each other cauſes the beginning branches to thicken and elongate into trees and ſhrubs rooted on the mercury. For other circumſtances concerning this beautiful experiment ſee Mr. Keir's Chemical Dictionary, art. Arbor Dianae; a work perhaps of greater utility to mankind than the loſt Alexandrian Library; the continuation of which is ſo eagerly expected by all, who are occupied in the arts, or attached to the ſciences.
THERE are four ſtrata of the atmoſphere, and four kinds of meteors. 1. Lightning is electric, exiſts in viſible clouds, its ſhort courſe, and red light. 2. Shooting ſtars exiſt in inviſible vapour, without ſound, white light, have no luminous trains. 3. Twi-light; fire-balls move thirty miles in a ſecond, and are about ſixty miles high, have luminous trains, occaſioned by an electric ſpark paſſing between the aerial and inflammable ſtrata of the atmoſphere, and mixing them and ſetting them on fire in its paſſage; attracted by volcanic eruptions; one thouſand miles through ſuch a medium reſiſts leſs than the tenth of an inch of glaſs. 4. Northern lights not attracted to a point but diffuſed; their colours; paſſage of electric fire in vacuo dubious; Dr. Franklin's theory of of northern lights countenanced in part by the ſuppoſition of a ſuperior atmoſphere of inflammable air; antiquity of their appearance; deſcribed in Maccabees.
THE rays refracted by the convexity of the atmoſphere; the particles of air and of water are blue; ſhadow by means of a candle in the day; halo round the moon in a fog; bright ſpot in the cornea of the eye; light from cat's eyes in the dark, from a horſe's eyes in a cavern, coloured by the choroid coat within the eye.
DISPUTE about phlogiſton; the ſun the fountain from whence all phlogiſton is derived; its rays not luminous till they arrive at our atmoſphere; light owing to their combuſtion with air, whence an unknown acid; the ſun is on fire only on its ſurface; the dark ſpots on it are excavations through its luminous cruſt.
SUN's heat much leſs than that from the fire at the earth's centre; ſun's heat penetrates but a few feet in ſummer; ſome mines are warm; warm ſprings owing to ſubterraneous fire; ſituations of volcanos on high mountains; original nucleus of the earth; deep vallies of the ocean; diſtant perception of earthquakes; great attraction of mountains; variation of the compaſs; countenance the exiſtence of a cavity or fluid lava within the earth.
COMBINED and ſenſible heat; chemical combinations attract heat, ſolutions reject heat; ice cools boiling water ſix times as much as cold water cools it; cold produced by evaporation; heat by devaporation; capacities of bodies in reſpect to heat, 1. Exiſtence of the matter of heat ſhewn from the mechanical condenſation and rarefaction of air, from the ſteam produced in exhauſting a receiver, ſnow from rarefied air, cold from diſcharging an air-gun, heat from vibration or friction; 2. Matter of heat analogous to the electric fluid in many circumſtances, explains many chemical phenomena.
MECHANICAL impulſe of light dubious; a glaſs tube laid horizontally before a fire revolves; pulſe-glaſs ſuſpended on a centre; black leather contracts in the ſunſhine; Memnon's ſtatue broken by Cambyſes.
EIGHTEEN ſpecies of glow-worm, their light owing to their reſpiration in tranſparent lungs; Acudia of Surinam gives light enough to read and draw by, uſe of its light to the inſect; luminous ſea-inſects adhere to the ſkin of thoſe who bathe in the ports of Languedoc, the light may ariſe from putreſcent ſlime.
DISCOVERED by Kunkel, Brandt, and Boyle; produced in reſpiration, and by luminous inſects, decayed wood, and calcined ſhells; bleaching a ſlow combuſtion in which the water is decompoſed; rancidity of animal fat owing to the decompoſition of water on its ſurface; aerated marine acid does not whiten or bleach the hand.
HERO of Alexandria firſt applied ſteam to machinery, next a French writer in 1630, the Marquis of Worceſter in 1655, Capt. Savery in 1689, Newcomen and Cawley added the piſton; the improvements of Watt and Boulton; power of one of their large engines equal to two hundred horſes.
EXPANSION of water in freezing; injury done by vernal froſts; fiſh, eggs, ſeeds, reſiſt congelation; animals do not reſiſt the increaſe of heat; froſts do not meliorate the ground, nor are in general ſalubrious; damp air produces cold on the ſkin by evaporation; ſnow leſs pernicious to agriculture than heavy rains for two reaſons.
1. Points preferable to knobs for defence of buildings; why points emit the electric fluid; diffuſion of oil on water; mountains are points on the earth's globe; do they produce aſcending currents of air? 2. Fairy-rings explained; advantage of paring and burning ground.
A TREE is a ſwarm of individual plants; vegetables are either oviparous or viviparous; are all annual productions like many kinds of inſects? Hybernacula, a new bark annually produced over the old one in trees and in ſome herbaceous plants, whence their roots ſeem end-bitten; all bulbous roots periſh annually; experiment on a tulip-root; both the leaf-bulbs and the flower-bulbs are annually renewed.
THE ſpots in the ſun are cavities, ſome of them four thouſand miles deep and many times as broad; internal parts of the ſun are not in a ſtate of combuſtion; volcanos viſible in the ſun; all the planets together are leſs than one ſix hundred and fiftieth part of the ſun; planets were ejected from the ſun by volcanos; many reaſons ſhewing the probability of this hypotheſis; Mr. Buffon's hypotheſis that planets were ſtruck off from the ſun by comets; why no new planets are ejected from the ſun; ſome comets and the georgium ſidus may be of later date; Sun's matter decreaſed; Mr. Ludlam's opinion, that it is poſſible the moon might be projected from the earth.
HIGH mountains and deep mines replete with ſhells; the earth's nucleus covered with limeſtone; animals convert water into limeſtone; all the calcareous earth in the world formed in animal and vegetable bodies; ſolid parts of the earth increaſe; the water decreaſes; tops of calcareous mountains diſſolved; whence ſpar, marbles, chalk, ſtalactites; whence alabaſter, fluor, flint, granulated limeſtone, from ſolution of their angles, and by attrition; tupha depoſited on moſs; limeſtones from ſhells with animals [Page 120] in them; liver-ſtone from freſh-water muſcles; calcareous earth from land-animals and vegetables, as marl; beds of marble ſoftened by fire; whence Bath-ſtone contains lime as well as limeſtone.
THE production of moraſſes from fallen woods; account by the Earl Cromartie of a new moraſs; moraſſes loſe their ſalts by ſolution in water; then their iron; their vegetable acid is converted into marine, nitrous, and vitriolic acids; whence gypſum, alum, ſulphur; into fluor-acid, whence fluor; into ſiliceous acid, whence flint, the ſand of the ſea, and other ſtrata of ſiliceous ſand and marl; ſome moraſſes ferment like new hay, and, ſubliming their phlogiſtic part, form coal-beds above and clay below, which are alſo produced by elutriation; ſhell-fiſh in ſome moraſſes, hence ſhells ſometimes found on coals and over iron-ſtone.
CALCIFORM ores; combuſtion of iron in vital air; ſteel from deprivation of vital air; welding; hardneſs; brittleneſs like Rupert's drops; ſpecific levity; hardneſs and brittleneſs compared; ſteel tempered by its colours; modern production of iron, manganeſe, calamy; ſeptaria of iron-ſtone ejected from volcanos; red-hot cannon balls.
1. Siliceous rocks from moraſſes; their cements. 2. Siliceous trees; coloured by iron or manganeſe; Peak-diamonds; Briſtol-ſtones; flint in form of calcareous ſpar; has been fluid without much heat; obtained from powdered quartz and fluor-acid by Bergman and by Achard. 3. Agates and onyxes found in ſand-rocks; of vegetable origin; have been in complete fuſion; their concentric coloured circles not from ſuperinduction but from congelation; experiment of freezing a ſolution of blue vitriol; iron and manganeſe repelled in ſpheres as the nodule of flint cooled; circular ſtains of marl in ſalt-mines; ſome flint nodules reſemble knots of wood or roots. 4. Sand of the ſea its acid from moraſſes; its baſe from ſhells. 5. Chert or petroſilex ſtratified in cooling; their colour and their acid from ſea-animals; labradore-ſtone from mother-pearl. 6. Flints in chalk-beds; their form, colour, and acid, from the fleſh of ſea-animals; ſome are hollow and lined with cryſtals; contain iron; not produced by injection from without; coralloids converted to flint; French-millſtones; flints ſometimes found in ſolid ſtrata. 7. Angles of ſand deſtroyed by attrition and ſolution in ſteam; ſiliceous breccia cemented by ſolution in red-hot water. 8. Baſaltes and granites are antient lavas; baſaltes raiſed by its congelation not by ſubterraneous fire.
FIRE and water two great agents; ſtratification from precipitation; many ſtratified materials not ſoluble in water. 1. Stratification of lava from ſucceſſive accumulation. 2. Stratifications of limeſtone from the different periods of time in which the ſhells were [Page 121] depoſited. 3. Stratifications of coal, and clay, and ſandſtone, and iron-ores, not from currents of water, but from the production of moraſs-beds at different periods of time; moraſs-beds become ignited; their bitumen and ſulphur is ſublimed; the clay, lime, and iron remain; whence ſand, marle, coal, white clay in valleys, and gravel-beds, and ſome ochres, and ſome calcareous depoſitions owing to alluviation; clay from decompoſed granite; from the lava of Veſuvius; from vitreous lavas.
ROSE-COLOUR and purple from gold; precipitates of gold by alcaline ſalt preferable to thoſe by tin; aurum fulminans long ground; tender colours from gold or iron not diſſolved but ſuſpended in the glaſs; cobalts; calces of cobalt and copper require a ſtrong fire; Ka-o-lin and Pe-tun-tſe the ſame as our own materials.
ITS figures do not allude to private hiſtory; they repreſent a part of the Eluſinian myſteries; marriage of Cupid and Pſyche; proceſſion of torches; the figures in one compartment repreſent MORTAL LIFE in the act of expiring, and HUMANKIND attending to her with concern; Adam and Eve hyeroglyphic figures; Abel and Cain other hyeroglyphic figures; on the other compartment is repreſented IMMORTAL LIFE, the Manes or Ghoſt deſcending into Eliſium is led on by DIVINE LOVE, and received by IMMORTAL LIFE, and conducted to Pluto; Tree of Life and Knowledge are emblematical; the figure at the bottom is of Atis, the firſt great Hierophant, or teacher of myſteries.
1. A fountain of foſſile tar in Shropſhire; has been diſtilled from the coal-beds beneath, and condenſed in the cavities of a ſand-rock; the coal beneath is deprived of its bitumen in part; bitumen ſublimed at Matlock into cavities lined with ſpar. 2. Coal has been expoſed to heat; woody fibres and vegetable ſeeds in coal at Bovey and Poleſworth; upper part of coal-beds more bituminous at Beaudeſert; thin ſtratum of aſphaltum near Caulk; upper part of coal-bed worſe at Alfreton; upper ſtratum of no value at Widdrington; alum at Weſt-Hallum; at Bilſton. 3. Coal at Coalbrooke-Dale has been immerſed in the ſea, ſhewn by ſea-ſhells; marks of violence in the colliery at Mendip and at Ticknal; Lead-ore and ſpar in coal-beds; gravel over coal near Lichfield; Coal produced from moraſſes ſhewn by fern-leaves, and bog-ſhells, and muſcle-ſhells; by ſome parts of coal being ſtill woody; from Lock Neagh and Bovey, and the Temple of the devil; fixed alcali; oil.
GRANITE the loweſt ſtratum of the earth yet known; porphory, trap, Moor-ſtone, Whin-ſtone, ſlate, baſaltes, all volcanic productions diſſolved in red-hot water; volcanos in granite ſtrata; differ from the heat of moraſſes from fermentation; the [Page 122] nucleus of the earth ejected from the ſun? was the ſun originally a planet? suppoſed ſection of the globe.
I. Solution of water in air; in the matter of heat; pulſe-glaſs. 2. Heat is the principal cauſe of evaporation; thermometer cooled by evaporation of ether; heat given from ſteam to the worm-tub; warmth accompanying rain. 3. Steam condenſed on the eduction of heat; moiſture on cold walls; ſouth-weſt and north-eaſt winds. 4. Solution of ſalt and of blue vitriol in the matter of heat. II. Other vapours may precipitate ſteam and form rain. 1. Cold the principal cauſe of devaporation; hence the ſteam diſſolved in heat is precipitated, but that diſſolved in air remains even in froſts; ſouth-weſt wind. 2. North-eaſt winds mixing with ſouth-weſt winds produce rain; becauſe the cold particles of air of the north-eaſt acquire ſome of the matter of heat from the ſouth-weſt winds. 3. Devaporation from mechanical expanſion of air, as in the receiver of an air-pump; ſummer-clouds appear and vaniſh; when the barometers ſink without change of wind the weather becomes colder. 4. Solution of water in electric fluid dubious. 5. Barometer ſinks from the leſſened gravity of the air, and from the rain having leſs preſſure as it falls; a mixture of a ſolution of water in calorique with an aerial ſolution of water is lighter than dry air; breath of animals in cold weather why condenſed into viſible vapour and diſſolved again.
LOWEST ſtrata of the earth appear on the higheſt hills; ſprings from dews ſliding between them; mountains are colder than plains; 1. from their being inſulated in the air; 2. from their enlarged ſurface; 3. from the rarety of the air it becomes a better conductor of heat; 4. by the air on mountains being mechanically rarefied as it aſcends; 5. gravitation of the matter of heat; 6. the daſhing of clouds againſt hills; of fogs againſt trees; ſprings ſtronger in hot days with cold nights; ſtreams from ſubterranean caverns; from beneath the ſnow on the Alps.
THE armour of the Echinus moveable; holds itſelf in ſtorms to ſtones by 1200 or 2000 ſtrings: Nautilus rows and ſails; renders its ſhell buoyant: Pinna and Cancer; Byſſus of the antients was the beard of the Pinna; as fine as the ſilk is ſpun by the ſilk-worm; gloves made of it; the beard of muſcles produces ſickneſs; Indian weed; tendons of rats tails.
STURGEON's mouth like a purſe; without teeth; tendrils like worms hang before his lips, which entice ſmall fiſh and ſea-inſects miſtaking them for worms; his ſkin uſed for covering carriages; iſinglaſs made from it; caviare from the ſpawn.
OIL and water do not touch; a ſecond drop of oil will not diffuſe itſelf on the preceeding one; hence it ſtills the waves; divers for pearl carry oil in their mouths; oil on water produces priſmatic colours; oiled cork circulates on water; a phial of oil and water made to oſcillate.
THE Teredo has calcareous jaws; a new enemy; they periſh when they meet together in their ligneous canals; United Provinces alarmed for the piles of the banks of Zeland; were deſtroyed by a ſevere winter.
A WHIRLPOOL on the coaſt of Norway; paſſes through a ſubterraneous cavity; leſs violent when the tide is up; eddies become hollow in the middle; heavy bodies are thrown out by eddies; light ones retained; oil and water whirled in a phial; hurricanes explained.
SNOW in contact with the earth is in a ſtate of thaw; ice-houſes; rivers from beneath the ſnow; rime in ſpring vaniſhes by its contact with the earth; and ſnow by its evaporation and contact with the earth; moſs vegetates beneath the ſnow; and Alpine plants periſh at Upſal for want of ſnow.
AIR is perpetually ſubject to increaſe and to diminution; Oxygene is perpetually produced from vegetables in the ſunſhine, and from clouds in the light, and from water; Azote is perpetually produced from animal and vegetable putrefaction, or combuſtion; from ſprings of water; volatile alcali; fixed alcali; ſea-water; the y are both perpetually diminiſhed by their contact with the ſoil, producing nitre; Oxygene is diminiſhed in the production of all acids; Azote by the growth of animal bodies; charcoal in burning conſumes double its weight of pure air; every barrel of red-lead abſorbes 2000 cubic feet of vital air; air obtained from variety of ſubſtances by Dr. Prieſtley; Officina aeris in the polar circle, and at the Line. South-weſt winds; their weſterly direction from the leſs velocity of the earth's ſurface; the contrary in reſpect to north-eaſt winds; South-weſt winds conſiſt of regions of air from the ſouth; and north-eaſt winds of regions of air from the north; when the ſouth-weſt prevails for weeks and the barometer ſinks to 28, what becomes of above one fifteenth part of the atmoſphere; 1. It is not carried back by ſuperior currents; 2. Not from its loſs of moiſture; 3. Not carried over the pole; 4. Not owing to atmoſpheric tides or mountains; 5. It is abſorbed at the polar circle; hence ſouth-weſt winds and rain; ſouth-weſt ſometimes cold. North-eaſt winds conſiſt of air from the north; cold by the evaporation of ice; are dry winds; 1. Not ſupplied [Page 124] by ſuperior currents; 2. The whole atmoſphere increaſed in quantity by air ſet at liberty from its combinations in the polar circles. South-eaſt winds conſiſt of north winds driven back. North-weſt winds conſiſt of ſouth-weſt winds driven back; north-weſt winds of America bring froſt; owing to a vertical ſpiral eddy of air between the eaſtern coaſt and the Apalachian mountains; hence the greater cold of North America. Trade-winds; air over the Line always hotter than at the tropics; trade-winds gain their eaſterly direction from the greater velocity of the earth's ſurface at the line; not ſupplied by ſuperior currents; ſupplied by decompoſed water in the ſun's great light; 1. Becauſe there are no conſtant rains in the tract of the trade-winds; 2. Becauſe there is no condenſible vapour above three or four miles high at the line. Monſoons and tornadoes; ſome places at the tropic become warmer when the ſun is vertical than at the line; hence the air aſcends, ſupplied on one ſide by the north-eaſt winds, and on the other by the ſouth-weſt; whence an aſcending eddy or tornado, raiſing water from the ſea, or ſand from the deſert, and inceſſant rains; air diminiſhed to the northward produces ſouth-weſt winds; tornadoes from heavier air above ſinking through lighter air below, which riſes through a perforation; hence trees are thrown down in a narrow line of twenty or forty yards broad, the ſea riſes like a cone, with great rain and lightning. Land and ſea breezes; ſea leſs heated than land; tropical iſlands more heated in the day than the ſea, and are cooled more in the night. Concluſion; irregular winds from other cauſes; only two original winds north and ſouth; different ſounds of north-eaſt and ſouth-weſt winds; a Bear or Dragon in the arctic circle that ſwallows at times and diſembogues again above one fifteenth part of the atmoſphere; wind-inſtruments; recapitulation.
PURE air from Dr. Prieſtley's vegetable matter, and from vegetable leaves, owing to decompoſition of water; the hydrogene retained by the vegetables; plants in the ſhade are tanned green by the ſun's light; animal ſkins are tanned yellow by the retention of hydrogene; much pure air from dew on a funny morning; bleaching why ſooner performed on cotton than linen; bees wax bleached; metals calcined by decompoſition of water; oil bleached in the light becomes yellow again in the dark; nitrous acid coloured by being expoſed to the ſun; vegetables perſpire more than animals, hence in the ſunſhine they purify air more by their perſpiration than they injure it by their reſpiration; they grow faſteſt in their ſleep.
BUDS the viviparous offſpring of vegetables; placentation in bulbs and feeds; placentation of buds in the roots, hence the riſing of ſap in the ſpring, as in vines, birch, which ceaſes as ſoon as the leaves expand; production of the leaf of Horſe-cheſnut, and of its new bud; oil of vitriol on the bud of Mimoſa killed the leaf alſo; placentation ſhewn from the ſweetneſs of the ſap; no umbilical artery in vegetables.
BUDS ſet in the ground will grow if prevented from bleeding to death by a cement; vegetables require no muſcles of locomotion, no ſtomach or bowels, no general ſyſtem of veins; they have, 1. Three ſyſtems of abſorbent veſſels; 2. Two pulmonary ſyſtems; 3. Arterial ſyſtems; 4. Glands; 5. Organs of reproduction; 6. muſcles. I. Abſorbent ſyſtem evinced by experiments by coloured abſorptions in fig-tree and picris; called air-veſſels erroneouſly; ſpiral ſtructure of abſorbent veſſels; retrograde motion of them like the throats of cows. II. Pulmonary arteries in the leaves, and pulmonary veins; no general ſyſtem of veins ſhewn by experiment; no heart; the arteries act like the vena portarum of the liver; pulmonary ſyſtem in the petals of flowers; circulation owing to living irritability; vegetable abſorption more powerful than animal, as in vines; not by capillary attraction.
I. Leaves not perſpiratory organs, nor excretory ones; lungs of animals. 1. Great ſurfaces of leaves. 2. Vegetable blood changes colour in the leaves; experiment with ſpurge; with picris. 3. Upper ſurface of the leaf only acts as a reſpiratory organ. 4. Upper ſurface repels moiſture; leaves laid on water. 5. Leaves killed by oil like inſects; muſcles at the foot-ſtalks of leaves. 6. Uſe of light to vegetable leaves; experiments of Prieſtley, Ingenhouze, and Scheel. 7. Vegetable circulation ſimilar to that of fiſh. II. Another pulmonary ſyſtem belongs to flowers; colours of flowers. 1. Vaſcular ſtructure of the corol. 2. Glands producing honey, wax, &c. periſh with the corol. 3. Many flowers have no green leaves attending them, as Colchicum. 4. Corols not for the defence of the ſtamens. 5. Corol of Helleborus Niger changes to a calyx. 6. Green leaves not neceſſary to the fruit-bud; green leaves of Colchicum belong to the new bulb not to the flower. 7. Flower-bud after the corol falls is ſimply an uterus; mature flowers not injured by taking of the green leaves. 8. Inoſculation of vegetable veſſels.
SEEDS in broom diſcovered twenty days before the flower opens; progreſs of the ſeed after impregnation; ſeeds exiſt before fecundation; analogy between ſeeds and eggs; progreſs of the egg within the hen; ſpawn of frogs and of fiſh; male Salamander; marine plants project a liquor not a powder; ſeminal fluid diluted with water, if a ſtimulus only? Male and female influence neceſſary in animals, inſects, and vegetables, both in production of feeds and buds; does the embryon feed produce the ſurrounding fruit, like inſects in gall-nuts?
VEGETABLE glands cannot be injected with coloured fluids; eſſential oil; wax; honey; nectary, its complicate apparatus; expoſes the honey to the air like the lacrymal gland; honey is nutritious; the male and female parts of flowers copulate and die like moths and butterflies, and are fed like them with honey; anthers ſuppoſed to become inſects; depredation of the honey and wax injurious to plants; honey-dew; honey oxygenated by expoſure to air; neceſſary for the production of ſenſibility; the proviſion for the embryon plant of honey, ſugar, ſtarch, &c. ſupplies food to numerous claſſes of animals; various vegetable ſecretions as gum tragacanth, camphor, elemi, anime, turpentine, balſam of Mecca, aloe, myrrh, elaſtic reſin, manna, ſugar, wax, tallow, and many other concrete juices; vegetable digeſtion; chemical production of ſugar would multiply mankind; economy of nature.THE END.
- Page 34. l. 354. for the read her.
- 37. l. 379. for burſts read burſt.
- 41. l. 423. for wirh read with.
- 58. At the end of the Argument, inſtead of "Departure of the Gnomes" pleaſe to add Tranſmigration of matter, 575.
- Page 76. inſtead of III. put 3.
- 80. inſtead of IV. put 4.
- 144. l. 376. for ſhut read ſhuts.
- 147. l. 423. for ſinking read ſhrinking.
- 170. l. 110. for her read its.
- 190. l. 359. for decry'd read deſcry'd.
- 204. l. 530. for nectarous read nectareous.
In the Additional Notes.
VIVUNT IN VENEREM FRONDES; NEMUS OMNE PER ALTUMFELIX ARBOR AMAT; NUTANT AD MUTUA PALMAEFAEDERA, POPULEO SUSPIRAT POPULUS ICTU,ET PLATANI PLATANIS, ALNOQUE ASSIBILAT ALNUS.CLAUD. EPITH.
THE general deſign of the following ſheets is to inliſt Imagination under the banner of Science, and to lead her votaries from the looſer analogies, which dreſs out the imagery of poetry, to the ſtricter ones, which form the ratiocination of philoſophy. While their particular deſign is to induce the ingenious to cultivate the knowledge of BOTANY; by introducing them to the veſtibule of that delightful ſcience, and recommending to their attention the immortal works of the Swediſh Naturaliſt LINNEUS.
In the firſt Poem, or Economy of Vegetation, the phyſiology of Plants is delivered; and the operation of the Elements, as far as they may be ſuppoſed to affect the growth of Vegetables. But the publication of this part is deferred to another year, for the purpoſe of repeating ſome experiments on vegetation, mentioned in the notes. In the ſecond poem, or LOVES OF THE PLANTS, which is here preſented to the Reader, the Sexual Syſtem of LINNEUS is explained, with the remarkable properties of many particular plants.
The author has withheld this work, (excepting a few pages) many years from the preſs, according to the rule of Horace, hoping to have rendered it more worthy the acceptance of the public,—but finds at length, that he is leſs able, from diſuſe, to correct the poetry; and, from want of leizure, to amplify the annotations.
In this ſecond edition, the plants Amaryllis, Orchis, and Cannabis are inſerted with two additional prints of flowers; ſome alterations are made in Glorioſa, and Tulipa; and the deſcription of the Saltmines in Poland is removed to the firſt poem on the Economy of Vegetation.
LINNEUS has divided the vegetable world into 24 Claſſes; theſe Claſſes into about 120 Orders; theſe Orders contain about 2000 Families, or Genera; and theſe Families about 20,000 Species; beſides the innumerable Varieties, which the accidents of climate or cultivation have added to theſe Species.
The Claſſes are diſtinguiſhed from each other in this ingenious ſyſtem, by the number, ſituation, adheſion, or reciprocal proportion of the males in each flower. The Orders, in many of theſe Claſſes, are diſtinguiſhed by the number, or other circumſtances of the females. The Families, or Genera, are characterized by the analogy of all the parts of the flower or fructification. The Species are diſtinguiſhed by the foliage of the plant; and the Varieties by any accidental circumſtance of colour, taſte, or odour; the ſeeds of theſe do not always produce plants ſimilar to the parent; as in our numerous fruit-trees and garden flowers; which are propagated by grafts or layers.
The firſt eleven Claſſes include the plants, in whoſe flowers both the ſexes reſide; and in which the Males or Stamens are neither united, nor unequal in height when at maturity; and are therefore diſtinguiſhed from each other ſimply by the number of males in each flower, as is ſeen in the annexed PLATE, copied from the Dictionaire Botanique of M. BULLIARD, in which the numbers of each diviſion refer to the Botanic Claſſes.
- [Page iv] CLASS I. ONE MALE, Monandria; includes the plants which poſſes but One Stamen in each flower.
- II. Two MALES, Diandria. Two Stamens.
- III. THREE MALES, Triandria. Three Stamens.
- IV. FOUR MALES, Tetrandria. Four Stamens.
- V. FIVE MALES, Pentandria. Five Stamens.
- VI. Six MALES, Hexandria. Six Stamens.
- VII. SEVEN MALES, Heptandria. Seven Stamens.
- VIII. EIGHT MALES, Octandria. Eight Stamens.
- IX. NINE MALES, Enneandria. Nine Stamens.
- X. TEN MALES, Decandria. Ten Stamens.
- XI. TWELVE MALES, Dodecandria. Twelve Stamens.
The next two Claſſes are diſtinguiſhed not only by the number of equal and diſunited males, as in the above eleven Claſſes, but require an additional circumſtance to be attended to, viz. whether the males or ſtamens be ſituated on the calyx, or not.
- XII. TWENTY MALES, Icoſandria. Twenty Stamens inſerted on the calyx or flower-cup; as is well ſeen in the laſt Figure of No. xii. in the annexed Plate.
- XIII. MANY MALES, Polyandria. From 20 to 100 Stamens, which do not adhere to the calyx; as is well ſeen in the firſt Figure of No. xiii. in the annexed Plate.
- XIV. Two POWERS, Didynamia. Four Stamens, of which two are lower than the other two; as is ſeen in the two firſt Figures of No. xiv.
- XV. FOUR POWERS, Tetradynamia. Six Stamens; of which four are taller, and the two lower ones oppoſite to each other; as is ſeen in the third Figure of the upper row in No. 15.
- XVI. ONE BROTHERHOOD, Monadelphia. Many Stamens united by their filaments into one company; as in the ſecond Figure below of No. xvi.
- XVII. Two BROTHERHOODS, Diadelphia. Many Stamens united by their filaments into two Companies; as in the uppermoſt Fig, No. xvii.
- XVIII. MANY BROTHERHOODS, Polyadelphia. Many Stamens united by their filaments into three or more companies, as in No. xviii.
- XIX. CONFEDERATE MALES, Syngeneſia. Many Stamens united by their anthers; as in firſt and ſecond Figures, No. xix.
- XX. FEMININE MALES, Gynandria. Many Stamens attached to the piſtil.
- XXI. ONE HOUSE, Monoecia. Male flowers and female flowers ſeparate, but on the ſame plant.
- XXII. Two HOUSES, Dioecia. Male flowers and female flowers ſeparate, on different plants.
- XXIII. POLYGAMY, Polygamia. Male and female flowers on one or more plants, which have at the ſame time flowers of both ſexes.
[Page vi] The Orders of the firſt thirteen Claſſes are founded on the number of Females, or Piſtils, and diſtinguiſhed by the names, ONE FEMALE, Monogynia. Two FEMALES, Digynia. THREE FEMALES, Trigynia. &c. as is ſeen in No. 1. which repreſents a plant of one male, one female; and in the firſt Figure of No. xi. which repreſents a flower with twelve males, and three females; (for, where the piſtils have no apparent ſtyles, the ſummits, or ſtigmas, are to be numbered) and in the firſt Figure of No. xii. which repreſents a flower with twenty males and many females; and in the laſt Figure of the ſame No. which has twenty males and one female; and in No. xiii. which repreſents a flower with many males and many females.
The Claſs of Two POWERS, is divided into two natural Orders; into ſuch as have their ſeeds naked at the bottom of the calyx, or flower cup; and ſuch as have their ſeeds covered; as is ſeen in No. xiv. Fig. 3. and 5.
The Claſs of FOUR POWERS, is divided alſo into two Orders; in one of theſe the ſeeds are incloſed in a ſilicule, as in Shepherd's purſe. No. xiv. Fig. 5. In the other they are incloſed in a ſilique, as in Wall-flower. Fig. 4.
In all the other Claſſes, excepting the Claſſes Confederate Males, and Clandeſtine Marriage, as the character of each Claſs is diſtinguiſhed by the ſituations of the males; the character of the Orders is marked by the numbers of them. In the Claſs ONE BROTHERHOOD, No. xvi. Fig. 3. the Order of ten males is repreſented. And in the Claſs Two BROTHERHOODS, No. xvii. Fig. 2. the Order ten males is repreſented.
The Orders are again divided into Genera, or Families, which are all natural aſſociations, and are deſcribed from the general reſemblances of the parts of fructification, in reſpect to their number, form, ſituation, and reciprocal proportion. Theſe are the Calyx, or Flowercup, as ſeen in No. iv. Fig. 1. No. x. Fig. 1. and 3. No. xiv. Fig. 1. 2. 3. 4. Second, the Corol, or Bloſſom, as ſeen in No. i. ii. &c. Third, the Males, or Stamens; as in No. iv. Fig. 1. and No. viii. Fig. 1. Fourth, the Females, or Piſtils; as in No. i. No. xii. Fig. 1. No. xiv. Fig. 3. No. xv. Fig. 3. Fifth, the Pericarp or Fruitveſſel; as No. xv. Fig. 4. 5. No. xvii. Fig. 2. Sixth, the Seeds.
The illuſtrious author of the Sexual Syſtem of Botany, in his preface to his account of the Natural Orders, ingeniouſly imagines, that one plant of each Natural Order was created in the beginning; and that the intermarriages of theſe produced one plant of every Genus, or Family; and that the intermarriages of theſe Generic, or Family plants, produced all the Species: and laſtly, that the intermarriages of the individuals of the Species produced the Varieties.
In the following POEM, the name or number of the Claſs or Order of each plant is printed in italics; as "Two brother ſwains." "One Houſe contains them." and the word "ſecret." expreſſes the Claſs of Clandeſtine Marriage.
The Reader, who wiſhes to become further acquainted with this delightful field of ſcience, is adviſed to ſtudy the words of the Great Maſter, and is apprized that they are exactly and literally tranſlated into Engliſh, by a Society at LICHFIELD, in four Volumes Octavo.
[Page viii] To the SYSTEM OF VEGETABLES is prefixed a copious explanation of all the Terms uſed in Botany, tranſlated from a theſis of Dr. ELMSGREEN, with the plates and references from the Philoſophia Botannica of LINNEUS.
To the FAMILIES OF PLANTS is prefixed a Catalogue of the names of plants, and other Botanic Terms, carefully accented, to ſhew their proper pronunciation; a work of great labour, and which was much wanted, not only by beginners, but by proficients in BOTANY.
Lo, here a CAMERA OBSCURA is preſented to thy view, in which are lights and ſhades dancing on a whited canvas, and magniſied into apparent life!—if thou art perfectly at leaſure for ſuch trivial amuſement, walk in, [Page x] and view the wonders of my INCHANTED GARDEN.
Whereas P. OVIDIUS NASO, a great Necromancer in the famous Court of AUGUSTUS CAESAR, did by art poetic tranſmute Men, Women, and even Gods and Goddeſſes, into Trees and Flowers; I have undertaken by ſimilar art to reſtore ſome of them to their original animality, after having remained priſoners ſo long in their reſpective vegetable manſions; and have here exhibited them before thee. Which thou may'ſt contemplate as diverſe little pictures ſuſpended over the chimney of a Lady's dreſſing-room, connected only by a ſlight feſtoon of ribbons. And which, [Page xi] though thou may'ſt not be acquainted with the originals, may amuſe thee by the beauty of their perſons, their graceful attitudes, or the brilliancy of their dreſs.
But in theſe lines below the perſon of Reaſon obtrudes itſelf into our company, and becomes diſagreeable by its diſtinctneſs, and conesquent improbability.—She never told her love;But let Concealment, like a worm i' th' bud,Feed on her damaſk cheek.—
Allegoric figures are on this account in general leſs manageable in painting and in ſtatuary than in poetry: and can ſeldom be introduced in the two former arts in company with natural figures, as is evident from the ridiculous effect of many of the paintings of Rubens in the Luxemburgh gallery; and for this reaſon, becauſe their improbability becomes more ſtriking, when there are the figures of real perſons by their ſide to compare them with. [Page 53] Mrs. Angelica Kauffman, well appriſed of this circumſtance, has introduced no mortal figures amongſt her Cupids and her Graces. And the great Roubiliac, in his unrivalled monument of Time and Fame ſtruggling for the trophy of General Fleming, has only hung up a medallion of the head of the hero of the piece. There are however ſome allegoric figures, which we have ſo often heard deſcribed or ſeen delineated, that we almoſt forget that they do not exiſt in common life; and hence view them without aſtoniſhment; as the figures of the heathen mythology, of angels, devils, death and time; and almoſt believe them to be realities, even when they are mixed with repreſentations of the natural forms of man. Whence I conclude, that a certain degree of probability is neceſſary to prevent us from revolting with diſtaſte from unnatural images; unleſs we are otherwiſe ſo much intereſted in the contemplation of them as not to perceive their improbability.To Reaſon I flew, and intreated her aid,Who pauſed on my caſe, and each circumſtance weigh'd;Then gravely reply'd in return to my prayer,That Hebe was faireſt of all that were fair.That's a truth, reply'd I, I've no need to be taught,I came to you, Reaſon, to find out a fault.If that's all, ſays Reaſon, return as you came,To find fault with Hebe would forfeit my name.