PHYSICAL SCIENCE AND CHRISTIAN REVELATION.
BY REV. JAMES A. STOTHERT.
II.
The advance of science has thrown some light on a subject of extreme difficulty and abstruseness: the relation of the qualities or accidents of matter to its substance. It is a subject of extreme difficulty, into which it seems not permitted to man to penetrate beyond the surface; but in regard to which much ignorance and misapprehension have been dispelled by the observations and deductions of modern philosophers. There are certain external marks or notes by which we recognize certain material things, as their form, their color, their hardness or softness, etc. One thing we call wood, another iron, a third wax, and so on. These external notes or marks by which we distinguish bodies are called their qualities, accidents, or properties. Underneath them there is the substance of the material thing, of which we have no means whatever of knowing anything. What it is that constitutes the difference between wood and iron, in their substance, must remain for ever a secret to our senses. We can perceive that one is harder, heavier, colder, then the other; but these observations go no further than the external qualities of the two bodies; regarding their absolute substance, or internal constitution, we have no possible means of forming a judgment. For all that we know, it may be the same in all bodies, or it may be as various as the simple elements of matter, now limited by chemists to about sixty, or it may be much more various. It is one of the mysteries of matter which will probably never be disclosed to the eye of man in this life.
Not only is the nature of material substance thus unknown to us, except through the external qualities, or accidents, which represent it; but we are informed by science that most of these qualities are the result of circumstances wholly distinct from their subject. A complete revolution in popular ideas has in part been achieved, in regard [{373}] to the permanence and immutability of these qualities of matter. Nothing seems more natural than to say that a red rose must be always red, a violet always blue, or that the size, shape, etc., of material bodies are inseparable from their existence. Yet Proteus himself was not more various in his shapes, than are the violet and the rose in the varieties of color of which they are so susceptible. Color, in fact, has no existence at all in the material object which we look at; it is a condition of the ray of light which enters our eye after reflection from the object, or after passing through it. Some objects absorb one or more parts of the three-fold visible ray of white light, and transmit or reflect to our eye only what remains of its constituent parts; some objects send the whole ray, undecomposed to the eye, and we call them white; others absorb it altogether, and they are said to be black. But all bodies, whatever their original color, that is, whatever part of the white ray they send to the eye, after absorbing the rest, may be made to appear of any color, by viewing them under the influence of variously colored light; which proves that their color exists not in themselves, but in the light which falls upon them, and on which their substance acts in some unknown way.
Sir John Herschel's testimony on this subject is very explicit. "Nothing at first can seem a more rational, obvious, and incontrovertible conclusion, then that the color of an object is an inherent quality, like its weight, hardness, etc.; and to see the object, and to see it of its own color, when nothing intervenes between our eyes and it, are one and the same thing. Yet this is only a prejudice; and that it is so is shown by bringing forward the same sense of vision which led to its adoption, as evidence on the other side; for when the differently colored prismatic rays are thrown, in a dark room, in succession upon any object, whatever be the color we are in the habit of calling its own, it will appear of the particular hue of the light which falls upon it: a yellow paper, for instance, will appear scarlet when illuminated by red rays; yellow, when by yellow; green, by green; and blue, by blue rays; its own (so called) proper color not in the least mixing with what it so exhibits." [Footnote 115] In like manner, other qualities of matter have no absolute existence, independent of circumstances. Twenty solid inches of sea water, if subjected to a pressure equal to that at a distance of twenty miles below the surface, would be reduced in volume to nineteen inches. [Footnote 116] A globe, an inch in diameter, consisting of air of the ordinary density at the earth's surface, if it could be removed into space one radius of the earth, say 4,000 miles, would expand into a sphere exceeding in radius the orbit of Saturn, as Sir Isaac Newton has calculated. Hence the tail of a great comet, such as that observed in 1843, and which extended from its nucleus 200 millions of miles, [Footnote 117] may, for aught we know, consist only of a very few pounds or even ounces of matter, expanded to a degree of tenuity to our minds almost inconceivable. [Footnote 118] The same agent, heat, modifies the extension and form of matter in totally opposite ways; making clay contract and lose in volume, while expanding water, and still more largely air. Extension, or form, therefore, is subject to great modification by change of circumstances; nor is weight less so. A pound weight of matter at the earth's equator weighs heavier at the poles; or, which is the same thing, a pendulum oscillates faster at the poles than at the equator. If removed to the planet Mars or Mercury, a pound of matter would lose half its weight; if to the surface of Jupiter, it would weigh nearly three times heavier.
[Footnote 115: Discourse, etc. §71.]
[Footnote 116: Somerville's Physical Geography, I., chap. xvi. p. 318.]
[Footnote 117: Hind's Comets, p. 22.]
[Footnote 118: Herschel's Outlines of Astronomy, chap. xi. §559, note.]
If there is one quality more than another characteristic of solid rock, it is the immobility of its parts; as mobility is a distinctive feature of water and vapor. Yet experiments in crystallization have demonstrated the existence of mobility even in solid bodies, in an unimaginable degree. Mrs. Somerville remarks, that "we are led, from the mobility of fluids, to expect great changes in the relative position of their molecules, which must be in perpetual motion, even in the stillest water and the calmest air; but we are not prepared to find motion to such an extent in the interior of solids. That their particles are brought nearer by cold and pressure, or removed further from one another by heat, might be expected; but it could not have been anticipated that their relative positions could be so entirely changed as to alter their mode of aggregation. It follows from the low temperature at which these changes are effected, that there is probably no position of inorganic matter that is not in a state of relative motion." [Footnote 119] And elsewhere, in her Physical Geography, the same high authority assures us that "nothing can be more certain than that the minute particles of matter are constantly in motion, from the action of heat, mutual attraction, and electricity. Prismatic crystals of salts of zinc are changed in a few seconds into crystals of a totally different form by the heat of the sun; casts of shells are found in rocks, from which the animal matter has been removed and its place supplied by mineral; and the excavations made in rocks diminish sensibly in size in a short time if the rock the soft, and in a longer time when it is hard; circumstances which show an intestine motion of the particles, not only in their relative positions, but in space, which there is every reason to believe is owing to electricity; a power which, if not the sole agent, must, at least, have cooperated essentially in the formation and filling of mineral veins." [Footnote 120]