Page:Popular Science Monthly Volume 31.djvu/522

506 as they clashed with one another in bodily impact around the central core. Each star, thus produced, forever gathers in materials from its own outlying mass, or from meteoric bodies, upon its solidifying nucleus, and forever radiates off its store of associated energy to the hypothetical surrounding ether. The fullest expression of this profound cosmical conception has been given in our own time by Tait and Balfour Stewart, working in part upon the previous results of Kant. Laplace, the Herschels, Mayer, Joule, Clerk Maxwell, and Sir William Thomson. Deeply altered as the nebular hypothesis has been by the modern doctrine of correlation and conservation of energies, and by modern researches into the nature of comets, meteors, and the sun's envelopes, it still remains in its ultimate essence the original theory of Kant and Laplace.

Science has thus, within the period of our own half-century, exhibited to us the existing phase of the universe at large in the light of an episode in a single infinite and picturable drama, setting out long since from a definite beginning, and tending slowly to a definite end. Other phases, inconceivable to us, may or may not possibly have preceded it; yet others, equally inconceivable, may or may not possibly follow. But as realizable to ourselves, within our existing limitations, the physical universe now reveals itself as starting in a remote past from a diffuse and perhaps nebulous condition, in which all the matter, reduced to a state of extreme tenuity, occupied immeasurably wide areas of space, while all the energy existed only in the potential forms as separation of atoms or molecules; and the evidence leads us to look forward to a remote future when all the matter shall be aggregated into its narrowest possible limits, while all the energy, having assumed the kinetic mode, shall have been radiated off into the ethereal medium. Compared to the infinite cosmical vistas thus laid open before our dazzled eyes, all the other scientific expansions of our age shrink into relative narrowness and insignificance.

As in the cosmos so in the solar system itself, evolutionism has taught us to regard our sun, with its attendant planets and their ancillary satellites, all in their several orbits, as owing their shape, size, relations, and movements, not to external design and deliberate creation, but to the slow and regular working out of physical laws, in accordance with which each has assumed its existing weight, and bulk, and path, and position.

Geology here takes up the evolutionary parable, and, accepting on trust from astronomy the earth itself as a cooling spheroid of incandescent matter, it has traced out the various steps by which the crust assumed its present form, and the continents and oceans their present distribution. Lyell here set on foot the evolutionary impulse. The researches of Scrope, Judd, and others into volcanic and hypogene action, and the long observations of geologists everywhere on the effects of air, rain, ice, rivers, lakes, and oceans, have resulted in