Page:Geology and Mineralogy considered with reference to Natural Theology, 1837, volume 1.djvu/59

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far we have been occupied with rocks, in which we trace chiefly the results of chemical and mechanical forces; but, as soon as we enter on the examination of strata of the Transition Series, the history of organic life becomes associated with that of mineral phenomena.

The mineral character of the transition formations presents alternations of slate and shale, with slaty sandstone, limestone, and conglomerate rocks; the latter bearing evidence of the action of water in violent motion; the former showing, by their composition and structure, and by the organic remains which they frequently contain, that they were for the most part deposited in the form of mud and sand, at the bottom of the sea.

Here, therefore, we enter on a new and no less curious than important field of inquiry, and commence our examination of the relics of a former world, with a view to ascertain how far the fossil members of the animal and vegetable kingdoms may, or may not, be related to existing genera and species, as parts of one great system of creation, all bearing marks of derivation from a common author.