stitution of Solar Light, by one of which it is considered to be comprised of different physical principles; and by the other it is supposed to consist of a number of distinct rays capable of being diversely deflected, and possessing different qualities according as they vary in refrangibility. Yet, by the adherents of both hypothesis it is admitted, that the solar rays do possess chemical properties. Heat, in Cab. Cyc. pp. 298-303, 399. Optics, idem, by Sir D. Brewster, pp. 90-93. Art. Light, in Dr. Ure's Chem. Dict. pp. 578580. Connexion of the Sciences, pp. 225-227. Daniel's Philos. of Chem. p. 456. Hunt on Light. Taylor's Scient. Mem. vol. iii. p. xi. Feb. 1843. De Luc's Letters, p. 78. Meteorology, by Dr. Thomson, 1849, p. 37, et seq. (founded on numerous concurring authorities). 41. That the surface, lengthways, of the solar spectrum is crossed by dark lines of different breadths, and amounting in number to nearly six hundred. That when sun or moonlight is employed in the experiment, their number, order, and intensity are found to be invariable. And that similar bands are perceived in light from the fixed stars, and from that afforded by electricity; but in the light given by a lamp or candle none of these fixed lines are perceptible. Optics, by Sir D. Brewster, Cab. Cyc. pp. 85—88, 142. Connexion of the Sciences, pp. 180-182. Astron. by Sir John Herschel, pp. 202, 203. Daniel's Philos. of Chem. pp. 183, 457. Hunt on Light, pp. 40, 41. Meteorology, by Dr. Thomson, 1849, p. 80. 42. That some late and delicate experiments in optics having proved that rays from the sun, even when transmitted obliquely, are not polarized, whereas those which emanate from encandescent bodies possess this remarkable property, it follows as a consequence, that solar light does not issue from an encandescent solid or fluid, but rather-as Herschel previously supposed-from an exterior film which is the source of its light; and that the intensity of the sun's light diminishes from the centre to the circumference of the solar disc. Astron. by Sir John Herschel, Cab. Cyc. p. 212. Whewell's Bridg. Treat. p. 171. Connexion of the Geol. by Dr. Ure, Intro. p. xxxvi. Prof. Heat, in Cab. Cyc. p. 314. Architec. idem, pp. 170-199. Meteorology, by Dr. Thomson, 1849, p. 83, et seq. Ꭰ 43. That common light moves in straight lines. That when it falls upon any surface, whether plane or curved, the angle of its reflection is equal to the angle of its incidence. That the intensity of radiant heat and light decreases in direct proportion to the square of the distance. And that one nonluminous body may receive light from another non-luminous body and discharge it upon a third; but in every case the light must come from a self-luminous body. Optics, by Sir D. Brewster, Cab. Cyc. pp. 1, 6, 23–25. Connexion of the Sciences, pp. 170-176, 189. Chemistry, in Cab. Cyc. p. 91. Astron. by Sir John Herschel, p. 212. Daniel's Philos. of Chem. p. 166. 44. That the following are some of the best ascertained effects of sunlight upon the vegetable kingdom, namely :— 1st. The quantity of water lost to a plant by evaporation, and its power of absorption from the soil are in proportion to the quantity of light. 2nd. Light causes the decomposition of the carbonic acid of vegetation; and, by solidifying the tissue, renders the parts most exposed to it the hardest. And 3rd. The green parts of plants, when exposed to the direct light of the sun, absorb from the atmosphere carbonic acid, which they decompose, and give back the oxygen. Botany, by Prof. Henslow, Cab. Cyc. pp. 92, 175, 186. Botany, in Lib. Useful Know. pp. 84-88. Hunt on Light, pp. 200—202. Meteorology, by Dr. Thomson, p. 15 (founded on numerous concurring evidences). 45. That two distinct hypothesis have been proposed respecting the nature of RADIANT HEAT. By one it is considered to be a material substance sui generis, capable of combining with other bodies, and by such combination producing the various effects attributed to heat. By the other it is regarded, not as a material substance, but as a quality of matter; bodies when heated being supposed to be in a certain state in which their constituent molecules, or the molecules of some subtle fluid which pervades them, are put into a state of vibration; and this vibration is considered the cause of heat. Heat, in Cab. Cyc. pp. 26, 379, 392–403. Chemistry, by Donovan, Cab. Cyc. pp. 40-42, 375–378. Daniel's Philos. of Chem. pp. 164, 208, 228, 685. Connexion of the Sciences, p. 411. Disc. on Nat. Philos. by Herschel, pp. 195, 310–323. Pollock's Attempt to Explain the Nature of Heat. 46. That the results of careful and repeated experiments prove, "that light and heat either do not possess the property of gravitation, or possess it in so small a degree as to be wholly inappreciable by any known means of measuring it." Connexion of the Sciences, pp. Heat, in Cab. Cyc. pp. 394–396. 239, 240. Chemistry, by Hugo Reid, p. 102. Chemistry, in Cab. Cyc. Hydro 47. That a comparison of the natural phenomena, in which the effects of LIGHT and HEAT are manifested, affords reason to infer the existence of a connexion so intimate between them as to warrant the belief of their identity. Nevertheless, although the instances are rare in which light does not emanate from incandescent bodies; yet, on the other hand, intense heat may be excited and communicated without being accompanied by visible light. Heat, in Cab. Cyc. pp. 22-25, 294, 339–353, 379–381, 398. A Paper read before the Royal Society by Herschel, May 15, 1800, p. 295. Dr. Faraday's Exper. Researches, vol. ii. System of Astronomy, by Margaret Bryan, 1797, pp. 5-15. Connexion of the Sciences, preface, also pp. 226-233, 237-249, 251, 355. Disc. on Nat. Philos. by Herschel, Cab. Cyc. p. 314. Prof. Whewell's Bridg. Treat. p. 136. Lectures at the Lond. Instit. by Prof. Grove, 1843 and 1844. Chemistry, in Cab. Cyc. pp. 40-42, 91. Hydrostatics, in idem. Electricity, in idem, pp. 162, 163. Daniel's Philos. of Chem. pp. 164-166, 208, 217. De Luc's Letters, pp. 76–80. 48. That by a concurring chain of deductive reasoning, drawn from the effects of the different heating powers of the component colours of the solar spectrum, when applied to substances reflecting various colours and degrees of heat; together with the corroborating testimony of the augmented heat of concentrated light, it is considered to be established, beyond the possibility of doubt, that, in these cases, sunlight is the direct cause of heat. Heat, in Cab. Cyc. pp. 345–350, 382. Connexion of the Sciences, p. 229. 209. 49. That the attraction of affinity-distinct from that of cohesion, and the highest degree of heterogeneous attraction, its ratios being determinate quantities-is supposed to be coexistent with matter. That it is one of the few forces known to act by election, and is productive of the most important results in nature. And, that during chemical action, heat is either developed or absorbed; whilst caloric and water are the agents most usually employed to facilitate and conduct chemical operations. Heat, in Cab. Cyc. pp. 3, 21, 25, 191-193, 294-296, 310, 354, 387. Disc. on Nat. Philos. in Cab. Cyc. pp. 310-313. Caloric and Combustion, Ure's Chem. Dict. pp. 353, 368. Chemistry, by Hugo Reid, p. 22, et seq. Connexion of the Sciences, p. 225. Chemistry, in Cab. Cyc. pp. 23-27, 384-386, et seq. Electricity, in idem, p. 162. Daniel's Philos. of Chemistry, pp. 101, 219, 306, 325, 338, 397, 444, 523, 685. Physiol. and Anatomy of Man, by Todd and Bowman, London, 1845, vol. i. pp. 2, 3, et seq. Dr. Faraday's Chem. Manipulations. 50. That the first and most usual effect of heat is to increase the size of the bodies to which it is imparted, by causing them to dilate or expand. That, although these effects are produced in different degrees and by different methods, according as the body to which heat is applied be solid, liquid, or aeriform, yet it may be considered as a physical law to which there is no real exception, that an increase in the temperature will be accompanied by an increase of volume, and a diminution of temperature by a diminution of volume. And that the force with which solids and liquids expand or contract by heat or cold is prodigious. Heat, in Cab. Cyc. pp. 8—10, 28—83, 162, 173-175, 187-189, 393. Connexion of the Sciences, pp. 117-120, 243. Chemistry, by Hugo Reid, pp. 22, 23. Mechanics, in Cab. Cyc. pp. 19, 20. Heat, in Chem. Dict. pp. 253-255, 278. Disc. on Nat. Philos. in Cab. Cyc. pp. 319322, 343. Chemistry, in Cab. Cyc. pp. 10, 42-48, 54-58. Daniel's Chem. Philos. pp. 685-687. Meteorology, by Dr. Thomson, 1849, p. 98, et seq. 51. That the phenomena arising from attraction and those from repulsion indicate the presence of two antagonist forces acting at the same time on the particles of all bodies, and maintaining them in a state of equilibrium; which becomes more or less disturbed according as either of these forces preponderates. Heat, in Cab. Cyc. pp. 2, 8, 11, 17, 185-199, 343. Cab. Cyc. pp. 89, 321. Chemistry, by Disc. on Nat. Philos. by Sir John Herschel, Connexion of the Sciences, pp. 117, 241–243. Chemistry, in Cab. Cyc. pp. 37-44, 49, 58. Hydrostatics, in idem, p. Electricity, in idem, pp. 225, 226. Daniel's Philos. of Chemistry, pp. 13, 17, 99, 450. Mechanics, in Cab. Cyc. pp. 8, 67. Meteorology, by Dr. Thomson, 1849, p. 370. 2. 52. That an irresistible body of analogies leads to the conviction, that the same physical properties, which observation and experience disclose in the smaller masses immediately surrounding us, are possessed by the infinite systems of bodies which fill the immensity of space. That the distribution of heat is regulated by the same laws amongst the bodies of the universe as among those which exist on our globe. That the earth absorbs and radiates heat in the same manner as every body on its surface, and therefore, if there were no external source of heat, the earth would be gradually cooled down and the temperature of all bodies would fall indefinitely. Heat, in Cab. Cyc. pp. 186, 379-382. Prof. Whewell's Bridg. Treat. p. 76. Dr. Faraday's Researches, vol. ii. pp. 284-293. Daniel's Philos. of Chem. p. 215. Constitut. Sidereal System, Lond. Edin. and Dub. Mag. Feb. 1843. Connexion of the Sciences, pp. 29, 363, 381-389, 401-411. Mechanics, in Cab. Cyc. p. 80. Architect. of the Heavens, Nichol, 1837. Phen. and Order of the Solar System, pp. 218-234. 53. That when a liquid passes into a solid state a sudden and considerable change of dimension is frequently observed; and that it may be considered as a general truth, to which, however, there are exceptions, that bodies which crystallize when they freeze, expand in doing so; while bodies which do not crystallize in solidifying, for the most part suffer contraction. Heat, in Cab. Cyc. pp. 128-131. Chemistry, in idem, pp. 52-58. |