GEOLOGV. 117 



subject, a determination to give it a minute examination. It is our de- 

 sign to give these articles an elementary character, pursuing, as much as 

 possible, the order of things, as they would present themselves to an in- 

 dependent explorer, rather than follow the leadings of any particular wri- 

 ter or theorist. 



To the votary of science^ Geology presents numerous points of great 

 and absorbing interest. If the laboratory of the chemist is attractive on 

 account of its surprising developements, the new and unexpected com- 

 pounds which are there formed, and the singular relations which differ- 

 ent kinds of matter are found to hold towards each other, no less inter- 

 esting must be the study of the chemical and physical changes, which 

 have, for ages past, been taking place on so stupendous a scale in the 

 great world of nature, the evidences of which we perceive, in the altered 

 and disrupted rocky strata of the Earth, and in the widely diffused re- 

 mains of its own former inhabitants left imprinted on its solid skeleton. 

 By means of its ever-active internal fires, and external waters and atmos- 

 pheric agencies, it has, more than once, been made to change the condi- 

 tion of its outer crust, and, by means of its hidden electric energies, it 

 has filled many of the fissures m that crust with the richest metalic ores. 



To the political economist and citizen this science is of no less inter- 

 est and importance. Since two-thirds of the two hundred millions of 

 square miles, which the Earth's surface contains, are covered with wa- 

 ter, and, of the remaining one-third, a considerable portion is occupied 

 by burning sands, or rocky mountains, or is bound by an inhospitable 

 climate, and is therefore incapable of producing the means of subsis- 

 tance to man, it is an interesting question : '-How may the remainder be 

 made to sustain the largest possible population witli the greatest comfort 

 and advantage?" In this view of the subject, the nature of soils, their 

 productiveness, their improvement, and tlie extraction of its mineral treas- 

 ures from the bosom of the Earth, all acquire the highest degress of im- 

 portance^ 



1. The first circumstance, which would probably arrest the attention 

 of an independent observer, is that the materials, which compose the 

 Earth's surface as far as we can penetrate it, exist either in a compacted 

 and solid form constituting roch^ or in a finely divided and comparatively 

 loose state constituting soil. The latter, almost every where, covers 

 the former to various depths, sometimes extending downwards very far, 

 at others only a few inches, and at others being entirely wanting, so that 

 there the rock extends to the surface. In many cases the soils are plain- 

 ly seen to have been derived from rock of the same kind as that which 

 they overlie, having resulted from their disintegration. Thus we have, 



