In the prosecution of these researches... extraneous fossils were no longer regarded merely as subjects of natural history, but as memorials of revol… - Gideon Mantell

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.

Every artificial excavation—every well and cellar—every cut for a fort, common road, railway, or canal—every quarry—every tunnel through a mountain—and every pit and gallery of a mine bored into the solid earth, furnish means of investigating its interior. Still more do the inland precipices, and the rocky promontories and headlands along the rivers, lakes, seas, and oceans; the naked mountain-sides ribbed with strata, that bound the defiles, gorges, and valleys; the ruins accumulated at the feet of lofty pinnacles and barriers, and those that have been transported and scattered, far and wide, over the earth; present us with striking features of the internal structure of our planet. Most of all, do the inclined strata push up their hard edges, in varied succession, and thus faithfully disclose the form and substance of the deep interior, as it exists many miles and leagues beneath the observer's feet.

Geology... possesses the great advantage of presenting subjects adapted to every capacity; on some of its investigations the highest intellectual powers and the most profound acquirements in exact science are required; while many of its problems may be solved by any one who has eyes and will use them; and innumerable facts illustrative of the ancient condition of our planet, and of its inhabitants, may be gathered by any diligent and intelligent observer.