tion.(5) Hence the previous atmosphere, which contains in it more than that portion, was indispensable, as was also some water on the soil where they were to grow.(6) This exact placing of the vegetable formation and first germination, is another test of the authenticity of the Hebrew cosmogony, which random fiction could not have stood. I was considerably affected in my younger days by the long standing objection, that Moses made light to exist before the creation of the sun, as books then usually taught, what some still fancy, that there could not have been light without this luminary. But not choosing on such an important point, to attach my faith to any general assertion, I sought to find out if any investigator of the nature of light had perceived any distinction in its qualities or operation, which made it a fluid, or matter, independent of the sun. It was not easy, before the year 1790, to meet with the works of any student of nature on such a subject, as it had been little attended to: but I at length saw the fact asserted by Henckel, a German of the old school, of some value in his day; and soon afterwards some experiments were announced in England, which confirmed the supposition. It has been a favorite point of attention with me ever since; and no truth dependently of their life, from the light and heat which are intimately connected with their existence and increase with their vigorous health. He doubts if those flowers are really luminious which have been marked as such, and concludes, from his experiments, that neither heat nor light are given out during the life of vegetables. Bull. Un. 1830, p. 257. In this conclusion I cannot concur, for I have at times remarked, after sunset, a perceptible glow in the colors of flowers, unusual to them in their common state, as if colored light of their own color was issuing from them. I have seen the difference in the sweet-williams, geraniums, marigolds, hearts-ease, and pinks, at various parts of the day, when the sun was not visible. It has been most apparent to me in the red flowers; next, in the yellow. It resembled an actual secretion of light, additional to their usual show. The presence of the sun upon them lessens the effect. It is most perceptible in his absence. I have noticed the same occasional appearance on the bricks in a country path. In some states of the atmosphere, when the sun was clouded, they have had a peculiar glow, without any visible causes. (5) The most favorable proportion is thought to be one fourth of oxygen, or that of the common air. Pure oxygen gas accelerates vegetation, but makes the plant feeble. In less than one eighth of oxygen, germination will not take place. (6) There is a remarkable connection between water and plants. Madden observed, in the deserts he traversed, that "wherever there is water, no matter in what part of the wilderness, there vegetables are found." Trav. in Turkey. in philosophy seems to be now more clearly ascertained, than that light has a distinct existence, separate and independent of the sun. This is a striking confirmation of the Mosaic record; for that expressly distinguishes the existence and operation of light from the solar action upon it, and from that radiation of it which is connected with his beams and presence. By Moses, an interval of three days is placed between the luminous creation, and the appearance and position of the sun and moon. Light was therefore operating, by its own laws and agencies, without the sun, and independently of his peculiar agency, from the first day to the fourth of our terrestrial fabrication. But from the time that the sun was placed in his central position, and his rays were appointed to act on our earth, they have been always performing most beneficial operations, essential to the general course of things.(7) They have also been ascertained, by Dr. Herschel, to have a power of heating, distinct from their production of light and color-an interesting discovery, connected with more consequences and inferences than have yet been noticed.(8) The glory of Sir Isaac Newton began by his discovering that light was not simple and homogeneous; but that it consisted of seven rays of different colors and of different and invariable degrees of refrangibility. The same degree of this belonged always to the same color, and the same color to the same degree of refrangibility.(9) Red, yellow, and blue, are the primary colors; white light, their compound. An opposing theory to this has been gradually growing up from the time of Des Cartes, and is now maintained by (7) "The rays of solar light possess several remarkable physical properties: they heat; they illuminate; they promote chemical combination; they effect chemical decompositions; they impart magnetism to steel; they alter the colors of bodies; they communicate to plants and flowers their peculiar colors; and are, in many cases, necessary to the development of their characteristic qualities." Dr. Brewster, Life of Newton, p. 90. (8) From his experiments, Dr. Herschel "drew the important conclusion, that there were invisible rays in the light of the sun, which had the power of producing heat; and which had a less degree of refrangibility than red light." These results were confirmed by Sir Henry Englefield Dr. Brewster's Optics, p. 89. (9) Brewster's Newton, p. 43. several men of no small name and powers in science,(10) which considers light to be an undulating vibration of an etherial medium universally diffused, and not, as Newton thought, an emanation of particles direct from the sun.(11) La Place preferred the opinion that "Light is an emanation from a luminous body."(12) But the newer system comes nearest to the Mosaic fact, that light was a distinct production anterior to the sun; and appears to be gaining ground in philosophical minds.(13) Perhaps some harmonizing combination of both theories may reconcile all the phenomena, and best explain the true nature and operation of light. It seems most probable that light is an etherial fluid now universally diffused, and pervading all things, and not an emanation from the sun; but that this luminary has a direct and additional agency upon it, whose effects we daily see. It may not be impertinent to suggest, that light seems, like heat, to have two states-active and latent. The active state causes its visible phenomena, and our sensation of daylight. When this subsides, by the sun's departure, into its latent state, our sense of darkness, or night, is produced. The solar rays again emerging on it, have the power of changing its latent state into its active visibility.(14) Light (10) Dr. Hooke, and Huygens, in Newton's lifetime, urged the undulatory theory which Des Cartes had first suggested. Newton answered them. But Euler and others revived it. New observations induced Dr. Young to adopt it, with very scientific illustrations. Since he wrote, Dufresnel, A. L. Cauchy, and M. Pouillet, have enforced it. Dr. Ure explains its modern shape at some length in his Geology. (11) Dr. Brewster thus briefly contrasts the two systems. "In the Newtonian theory, light is supposed to consist of material particles emitted by luminous bodies; and moving through space with a velocity of 192,000 miles in a second. In the undulatory theory, an exceedingly thin and elastic medium, called ether, is supposed to fill all space, and to occupy the intervals between the particles of all material bodies." Dr. Brewster's Optics, p. 134. (12) Syst. vol. 2, p. 91. (13) "Each of these two theories of light is beset with difficulties peculiar to itself: but the theory of undulation has made great progress in modern times; and derives such powerful support from an extensive class of phenomena, that it has been received by many of our most distinguished philosophers." Dr. Brewster's Optics, p. 135. (14) Fresnel says, on the new theory, "If the phenomena of light be considered as the vibrations of an elastic fluid, we may infer that the direction of these vibrations is perpendicular to that of the luminous ray. This is supposed on the idea that the different parts of an elastic fluid has also the property of being absorbed by, and, I would add, of combining with, all substances;(15) with some wholly, which are then black; with others, the most numerous cases, only in part; and then, that portion of them which is not so absorbed, emanates from the substance in the color which comes from them to our eye.(16) After having for many years attended to the phenomena of light, I cannot but consider it to be a universally diffused fluid. Thus far the idea would accord with the undulatory theory; but many facts led me also to conclude that it actually enters into the composition of all or of most substances, and, like heat, becomes a latent part of them.(17) From these it is extricable, with more or less rapidity, without the interference of the solar ray, as in the burning of all inflammable bodies, when it passes into its active and visible state. When the two liquids, of nitrous gas and oil of turpentine, burst into a flame on being mixed, without the approach of any fire, I think we see a striking instance of latent and combined light passing suddenly into the free and active state. So when that brilliant blaze occurs on dipping the iron wire into oxygen gas, it seems to be the latent light combined in the gas, evolving from it instantaneously into its visible form. act on each other by alternate compression and dilatation." Bull. Univ. 1830, p. 108. (15) "One of the most curious properties of bodies is their power of absorbing light. Charcoal is the most absorptive of all. Even the most transparent bodies in nature, air and water, when in sufficient thickness, are capable of absorbing a great quantity of light." Dr. Brewster, Opts. p. 137. (16) Sir I. Newton "concluded that the colors of natural bodies are not qualities inherent in the bodies themselves, but arise from the disposition of the particles of each body to stop or absorb certain rays; and thus to reflect more copiously, the rays which are not thus absorbed." Dr. Brewster's Life of Newton, p. 46. Bodies absorb light in different degrees, in this order: Charcoal, Coal of all kinds, Metals in general, Silver, Gold, Black hornblende, Mica, Glass, Ib. Opt. 137. (17) Dr. Brewster expresses the same idea, with which I have been for some time impressed: "Whatever be the difficulties which attach to the theory that supposes light to consist of material particles, we are compelled by its properties to admit, that light acts as if it were material; and that it enters into combinations with bodies, in order to produce the effects which we have enumerated." Life of Newton, p. 90. The sun has nothing to do with these phenomena, nor with any of our artificial illuminations. All these may be deemed latent light emerging from its combinations into free and active visibility. Yet most of the Newtonian principles and laws concerning it, are confirmed by the phenomena which suggested them; and so is much of the new system by those facts which have been adduced in its support.(18) Hence it is most probable that both theories have a foundation in truth, but require some further additions and modification on each side to make them con#istent with each other; and to remove the apparent contradictions which now keep them in the state of controversial hostility.(19) (18) Dr. Brewster has very ably distinguished the parts of the Newtonian doctrine of colors, which have been found strictly true, from those which later observations have disproved, and has added his own intelligent views of the new principles that have since been disclosed. Life of Newton, chap. 7. To our more correct knowledge of light, he has himself largely contributed. (19) We may again notice here the surprising demands which philosophy sometimes makes on the believing principle within us, and the willing credulity with which we receive its annunciations, while we erect ourselves so pugnaciously against the subjects of religious faith. Can any thing of this latter description more exceed our comprehending faculties, or more intensely press our believing ones, than what three men of great science and celebrity, Mr. Herschel, Dr. Young, and Dr. Brewster, with many similar collaborateurs, assure us to be true. I will state it in the words of the first, and add Dr. Young's illustrating calculations. "Modern optical discoveries have disclosed, that every point of a medium, through which a ray of light passes, is affected with a succession of periodical movements, regularly recurring at equal intervals; no less than 500 millions of millions of times in a single second. It is by such movements communicated to the nerves of our eyes, that we see." J. W. HERSCHEL'S Discourse, p. 24. Thus Dr. YOUNG tell us, that when we see the following colors, our eyes are affected in a second, that is, in one swing of a pendulum, or while we can pronounce one, In RED, 482 millions of millions of times; Lect. Nat. Phil. v. 2, p. 627. BLUE 622,000,000,000 Dr. Brewster's Optics, p. 136. Which exacts more of our faith, religion or philosophy? I think very often the latter. Why, then, more difficult in the one, than in the other? |