16 Feather stonhangh^s Geological Report. 



ciate strata. And thus, by travelling and practical investiga 

 tion, and by books and the conversation of experienced men, 

 the geological student at length comes to understand that the 

 earth is not a mass of rocks, clays, and sands, accumulated 

 without order and design, but that a portion of the superficial 

 part of the planet, now called the crust, is composed of a 

 series of strata, differing from each other in very material 

 circumstances, yet observing the same order of superposition 

 to each other at the greatest geographical distances, and hav 

 ing, of course, come into that order at successive periods. 

 Leaving the geological student to the impressions which 

 these appearances will make upon him, the various strata of 

 this series, as they have been observed both in Europe and 

 in the United States, and which comprehend the whole 

 rocky structure of the crust of the earth, as far as it has been 

 examined, will be briefly considered. It is stated in my 

 report of 1835,* that the whole of these rocks, considered as 

 a geological column, which, in one sense, as will be hereafter 

 shown, form a true geological column, may be subdivided 

 into two divisions ; the inferior, in which no animal or vege 

 table fossils have been observed, and therefore deemed to be 

 inorganic, and the superior, which is organic, because in it 

 those fossils abound. This last division is probably, in contra 

 distinction to the lowest rocks of the preceding division, of 

 aqueous origin, being constituted of the ruins of some of the 

 inferior rocks, brought into a comminuted state by the action 

 of water, which, when in a state of repose, subsequently 

 distributed them into levels. Other rocks are the result of 

 quiet depositions from mineral waters, and some may be the 

 result of copious ejections of mud from ancient volcanoes. 

 There is also another class of rocks, to which the term 

 &quot; intrusive rocks&quot; has been well applied. It is familiarly 

 known that modern volcanoes eject rocky matter in a mol- 



