“In the beginning God created the heaven and the earth.” MOSES. Geology is the history of the _crust_ of this planet. This history we compile, not from old records or moth-eaten state papers, not from antiquarian research or the study of ancient coins, but from actual and painstaking examination of the materials composing this crust. How suitable is this word _crust_, will be seen at once, when it is considered that its thickness in all probability does not exceed eighty miles, a mere fraction of the distance to the earth’s centre. Of this eighty miles we know pretty accurately the character and arrangement of some seven or eight miles; not that we have ever penetrated so far beneath the surface in a straight line, the deepest mines not exceeding 1800 or 1900 feet; but, by putting together the thicknesses of the various strata, with which we are well acquainted, we reach this conclusion without much hesitation. Professor Whewell has well observed, that “an earth greater or smaller, denser or rarer, than the one on which we live, would require a change in the structure and strength of all the little flowers that hang their heads under our hedges. There is something curious in thus considering the whole mass from pole to pole and from circumference to centre, as employed in keeping a snowdrop in the position most suited to its vegetable health.”[1] When we come to examine this crust, several appearances of a striking character reward our toil. At first, and before we proceed in our investigations more minutely, we find that there are only two varieties of rocks in all the vast arrangements spread out before us. Some rocks we find to be unstratified, and others we find to be stratified: from the absence of all fossils in the former of these, and from their crystalline character, we conclude that these were formed by the action of _fire_, and therefore we call them _Igneous_ or _Plutonic_ rocks. From the sedimentary character and from the numerous fossils of the stratified rocks, we conclude these to have been formed by the action of _water_, and we therefore call these _Aqueous_ or _Neptunian_ rocks. Following out these investigations, we meet with other facts equally interesting: we find that the Plutonic or unstratified rocks lie generally at the base of all the others, and that where they come up to the surface and crop out from other rocks, or rise in towering mountain heights above them, this has been the result of igneous action from beneath, and that this elevation has disturbed the surrounding strata from the horizontal position in which we imagine them to have been first arranged. The extent of the Plutonic rocks is immense; in _Europe_, the Scandinavian mountains, the Alps, the Pyrenees, and the Carpathians; in _Asia_, the Himalayan, the Caucasian, and the Altai mountains; in _Africa_, the Atlas mountains and the Cape of Good Hope; in _America_, nearly the