But even the said pebbly bed, like the hardest rock, like the seemingly everlasting granite, must and does change. The compact, chrystalline, azoic rock, without a trace of life in its dense mass, would eventually decompose if constantly assailed and affected by the moving waves of that gaseous ocean whose bed is formed by the terrestrial crust. If the rock is found covered by more or less stratified layers, its presence in the bosom of the earth will attest to passing generations the primordial incandescence of our planet at some epoch when life as yet was _not_,--when the liquid element, hurled far away into space under the form of vapour, exhibited the aspect of a "bearded meteor," or a comet, with blazing nucleus and incandescent tail. Many the changes which since that distant epoch have taken place upon the earth, and many more must occur before our planet ceases to contribute its strain to the grand harmony of the spheres. Our world will _end_ as surely as it once had a beginning: its duration, though it be computed by hundreds of thousands of years, is nothing, will be nothing, compared with that of the revolution of yonder sun, circling, with its wondrous train of planets, around some mysterious centre as yet unknown. And in this period, hitherto incalculable, what chances of perturbation will necessarily arise? Let us suppose that the centre around which oscillates, on the one part, the moon while drawing near and receding from the earth; on the other, the earth while drawing near and receding from the sun: let us suppose that these centres oscillate in the same manner around other centres as yet undetermined,--and this hypothesis is very rational, since it is based on the principle that everything moves or changes,--it may happen that in these periodical oscillations, one or more of the circulating masses will eventually fall into their focus of attraction, or will start so widely astray that the wheelwork of our world, the various parts of our planetary system, will separate,--not to be annihilated, for nothing in the universe can be _annihilated_,--but to be metamorphosed, and group themselves elsewhere in a different order.[87] It is thus that in chemistry, which I would call the _astronomy of atoms_, it is shown that bodies are only so far decomposed as to admit of their recombination in new forms; the end of one is the beginning of another. Now, that which is true of the systems of the elementary bodies composing terrestrial matter, is, in all probability, true also--why should it not be?--of the systems of the celestial bodies.