parallelism of their layers, which, in all their bendings, is so accurately preserved. It does, indeed, so little serve to explain these facts, that, were the appearances completely reversed; did the strata assume the most complex, instead of the most simple curvature; instead of equidistant, were they converging, or alternately receding and approaching to one another; the theory of crystallization might be equally applied to them. The state of the phenomena is a matter of perfect indifference to such a theory as this; all things are explained by it with the same facility; the straight and the crooked, the square and the round, the moveable and the immoveable. Is it not evident that such an explanation is a mere word; or, if any thing more than a word, an expression of our ignorance, so awkward and indirect, as to deprive us of whatever credit might have been gained by a plain and candid avowal of it? [Footnote 107: Voyages aux Alpes, tom. i. § 475.] It should never be forgotten, that a theory which accounts for _any thing_, and a theory which accounts for _nothing_, stand precisely on the same footing, and ought to be banished from all parts of philosophy, as they have been from those sciences which are justly honoured with the name of accurate. The animated orbs of Aristotle, and the vortices of Des Cartes, have long ceased to be mentioned in physical astronomy; the first, because, they accounted for every thing alike; the second, because, when they accounted for one thing, they never could be made to account for another. Both theories, therefore, have very properly been rejected; and, when geology shall undergo a similar purification, the principle we have been considering will not be the only sacrifice required of the Neptunian system. 209. An appearance observed in some kinds of primary schistus, which clearly indicates their deposition by water, and in planes very different from those in which we now see them, though it might have been introduced before, is also much connected with the present argument. This appearance consists of small wavings or undulæ on the surface of the plates of schistus, precisely similar to these marks which are left by the sea on a gently inclining beach of sand, at the ebbing of the tide. All the species of schistus do not seem to afford instances of these wavings. The rocks which do so, are, I think, chiefly of the argillaceous kind, but often highly indurated; so that the laminæ containing the impressions are not to be torn asunder but with great difficulty. Instances of it abound in the schistus of Berwickshire, and are also not unfrequent in that of Galloway. All must agree about the agent which produced these marks; it could be no other than the sea; but it must have been the sea acting on loose, small and round particles, lying on a surface which was nearly horizontal.