117. We are not, however, to imagine, that there is no where any means of repairing this waste; for, on comparing the conclusion at which we are now arrived, viz. that the present continents are all going to decay, and their materials descending into the ocean, with the proposition first laid down, that these same continents are composed of materials which must have been collected from the decay of former rocks, it is impossible not to recognise two corresponding steps of the same progress; of a progress, by which mineral substances are subjected to the same series of changes, and alternately wasted away and renovated. In the same manner, as the present mineral substances derive their origin from substances similar to themselves; so, from the land now going to decay, the sand and gravel forming on the sea shore, or in the beds of rivers; from the shells and corals, which in such enormous quantities are every day accumulated in the bosom of the sea; from the drift wood, and the multitude of vegetable and animal remains continually deposited in the ocean: from all these we cannot doubt, that strata are now forming in those regions, to which nature seems to have confined the powers of mineral reproduction; from which, after being consolidated, they are again destined to emerge, and to exhibit a series of changes similar to the past.[33] [Footnote 33: NOTE XIX.] 118. How often these vicissitudes of decay and renovation have been repeated, is not for us to determine: they constitute a series, of which, as the author of this theory has remarked, we neither see the beginning nor the end; a circumstance that accords well with what is known concerning other parts of the economy of the world. In the continuation of the different species of animals and vegetables that inhabit the earth, we discern neither a beginning nor an end; and, in the planetary motions, where geometry has carried the eye so far both into the future and the past, we discover no mark, either of the commencement or the termination of the present order.[34] It is unreasonable, indeed, to suppose, that such marks should any where exist. The Author of nature has not given laws to the universe, which, like the institutions of men, carry in themselves the elements of their own destruction. He has not permitted, in his works, any symptom of infancy or of old age, or any sign by which we may estimate either their fixture or their past duration. He may put an end, as be no doubt gave a beginning, to the present system, at some determinate period; but we may safely conclude, that this great _catastrophe_ will not be brought about by any of the laws now existing, and that it is not indicated by any thing which we perceive. [Footnote 34: NOTE XX.]