Geology, a term signifying a discourse on the Earth, (from two Greek words: viz. γἡ, _ge_, the earth; and λὁγος, _logos_, a discourse,) is the science which treats of the physical structure of the planet on which we live, and of the nature and causes of the successive changes which have taken place in the organic and inorganic kingdoms, from the remotest period to the present time, and is therefore intimately connected with every department of natural philosophy. While in common with other scientific pursuits it yields the noblest and purest pleasures of which the human mind is susceptible, it has peculiar claims on our attention, since it offers inexhaustible and varied fields of intellectual research, and its cultivation, beyond that of any other science, is in a great measure independent of external circumstances; for it can be followed in whatever condition of life we maybe placed, and wherever our fortunes may lead us. The eulogium passed by a distinguished living philosopher on scientific knowledge in general, is strikingly applicable to geological investigations. "The highest worldly-prosperity, so far from being incompatible with them, supplies additional advantages for their pursuit; they may be alike enjoyed in the intervals of the most active business, while the calm and dispassionate interest with which they fill the mind, renders them a most delightful retreat from the agitations and dissensions of the world, and from the conflict of passions, prejudices, and interests, in which the man of business finds himself continually involved."[2] [2] Sir J. F. W. Herschel, "Discourse on the Study of Natural Philosophy." From the present advanced state of geological science, particularly of that department which it is the more especial object of these volumes to elucidate, namely Palæontology,[3] or the study of Organic Remains,--it seems scarcely credible, that but little more than a century ago it was a matter of serious question with naturalists, whether the petrified shells imbedded in the rocks and strata were indeed shells that had been secreted by molluscous animals; or whether these bodies, together with the teeth, bones, leaves, wood, &c. found in a fossil state, were not formed by what was then termed the plastic power of the earth; in like manner as minerals, metals, and crystals. [3] Palæontology: from παλαιος, _palaios_, ancient--οντα, _onta_, beings--λὁγος, _logos_, a discourse.