136. In his Geological Essays, Mr Kirwan says, that "some geologists, as Buffon, and of late Dr Hutton, have excluded calcareous earth from the number of the primeval, asserting the masses of it we at present behold to proceed from shell-fish. But, in addition to the unfounded supposition, that shell-fish, or any animals, possess the power of producing any simple earth, these philosophers should have considered, that, before the existence of any fish, the stony masses that inclose the bason of the sea, must have existed; and, among these, there is none in which calcareous earth is not found. Dr Hutton endeavours to _evade_ this argument, by supposing the world we now inhabit to have arisen from the ruins and fragments of an anterior, without pointing at any original. If we are thus to proceed _in infinitum_, I shall not pretend to follow him; but, if he stops any where, he will find the same argument equally to occur."[45] [Footnote 45: Geol. Essays, p. 13.] The argument here employed would certainly be conclusive against any one, who, in disputing about the _first origin_ of things, should deny that the calcareous is as ancient as any other of the simple earths. But this has nothing to do with Dr Hutton's speculations, which, as has been just said, never extended to the _first origin_ of substances, but were confined entirely to their changes; so that what he asserts concerning the calcareous rocks, is no more than that those which we now see have been formed from loose materials, deposited at the bottom of the sea. It was not therefore in order to _evade_ Mr Kirwan's argument, as the preceding passage would lead us to believe, that he supposed the world which we now inhabit to have arisen from the ruin and waste of an anterior world; but it was because this seemed to him a conclusion which necessarily followed from the phenomena of geology, and it was a conclusion that he had deduced long before he heard of Mr Kirwan's objections to his system. Instead of an _evasion_, therefore, any one who considers the subject fairly, will see, in Dr Hutton's reasoning, nothing but the caution of a philosopher, who wisely confines his theory within the same limits by which nature has confined his experience and observation. It is nevertheless true, that Dr Hutton has sometimes expressed himself as if he thought that the present calcareous rocks are all composed of animal remains.[46] This conclusion, however, is more general than the facts warrant; and, from some incorrectness or ambiguity of language, is certainly more general than he intended. The idea of calcareous rocks, on which he argues throughout his whole theory, is precisely that which is stated in the preceding article. [Footnote 46: Theory of the Earth, vol. i. p. 23.] NOTE II. § 6. _Origin of coal._