Illustrations of the Huttonian Theory of the Earth

by John Playfair

Note i. § 2.

Origin of calcareous rocks.

135. I

134. IT has been asserted, that Dr Hutton went farther than is stated at § 2, and maintained all calcareous matter to be originally of animal formation. This position, however, is so far from being laid down by Dr Hutton, that it belongs to an inquiry which he carefully avoided to enter on, as being altogether beyond the limits of philosophical investigation.

He has indeed no where treated of the first origin of any of the earths, or of any substance whatsoever, but only of the transformations which bodies have undergone since the present laws of nature were established. He considered this last as all that a science, built on experiment and observation, can possibly extend to; and willingly left, to more presumptuous inquirers, the task of carrying their reasonings beyond the boundaries of nature, and of unfolding the properties of the chaotic fluid, with as much minuteness of detail, as if they were describing the circumstances of a chemical process which they had actually witnessed.

The idea of calcareous matter which really belongs to the Huttonian Theory, is, that in all the changes which the terraqueous globe has undergone in past ages, this matter existed, as it does now, either in the form of limestone and marble, or in the composition of other stones, or in the state of corals, shells, and bones of animals. It may be true, that there is no particle of calcareous matter, at present existing on the surface of the earth, that has not, at some time, made a part of an animal body; but of this we can have no certainty, nor is it of any importance that we should. It is enough to know, that the rocks of marble and limestone contain in general marks of having been formed from materials collected at the bottom of the sea; and of this a single cockle-shell, or piece of coral, found included in a rock, is a sufficient proof with respect to the whole mass of which it makes a part.

The principal object which Dr Hutton had in view when he spoke of the masses of marble and limestone, as composed of the calcareous matter of marine bodies,[43] was to prove, that they had been all formed at the bottom of the sea, and from materials there deposited. His general conclusion is, "That all the strata of the earth, not only those consisting of such calcareous masses, but others superincumbent upon these, have had their origin at the bottom of the sea, by the collection of sand and gravel, of shells, of coralline and crustaceous bodies, and of earths and clays variously mixed, or separated and accumulated. This is a general conclusion, well authenticated by the appearances of nature, and highly important in the natural history of the earth."[44]

[43] Theory of the Earth, vol. i. p. 23, 24.

[44] Theory of the Earth, vol. i. p. 26.

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]

[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.

[46] Theory of the Earth, vol. i. p. 23.