135. 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] [Footnote 43: Theory of the Earth, vol. i. p. 23, 24.] [Footnote 44: Theory of the Earth, vol. i. p. 26.]