lis GEOLOCr. 



covering a large portion of Adams county, a red soil derived from the 

 underlying New Red Sandstone. In many other cases, however, the 

 soils differ in their character from the rocks which they overlie, having 

 been brought from some distance by the transporting power of watei*. 

 Thus a limestone soil often covers a substratum of slate, having beea 

 brought from a neighboring limestone region. From this, it would ap- 

 pear that rocks and soils are composed of the same materials, the one 

 having been derived from the other. What are, then, these materials .-' 



Chemistry teaches us that there are sixty-one elementary substances 

 or different kinds of simple matter, of which forty-eight are metals. Of 

 these, combined in various proportions, all material bodies are composed. 

 Hut few of the metals are found pure in nature, being mostly in combi- 

 nation with oxygen, forming with itapulverulent substance called in sci- 

 entific language an oxide, but in common language an earth. These con- 

 stitute the rocks, soils, and the whole crust of the globe as far as our 

 knowledge of it extend.s, which is to the depth of from one-half of a 

 mile, by means of mines, and through the materials ejected from the cra- 

 ters of volcanos, to a much greater depth. 



It, however, by no means follows that each of these sixty-one ele- 

 ments enters into the composition of every rock and soil, or that they 

 arc alike abundant. The most abundant are Silica, silex or the principal 

 ingredient in pure sand. Alumina the principal ingredient in potters clay. 

 Lime, Magnesia, oxide of h-on, Potash and Soda. These constitute more 

 than- nineteen-twentieths of the crust of the globe, whilst a few of the 

 others, with the remains of animal and vegetable substances, of which 

 carbon is the most abundant, form the remaining one-twentieth. 



When two or more of these element are combined so as to produce a 

 substance homogenous in its appearance and other physical properties ills 

 called a simple JUmeraZ, although it be chemically compound. The most 

 common minerals arc Quartz, Felspar, Mica, Hornblende, Talc, Chlorite, 

 Limestone, Gypsum, and the oxides of Iron. Quartz or Silica is the pure 

 ingredient in flhit or sand, and is very extensively distributed over the 

 globe. There is scarcely a rock or soil from which it is entirely absent, 

 and no soil is fitted for vegetation without it, since it is an essential con- 

 stituent of many plants, especially of the grasses, reeds and cerealia. — 

 Felspar, (which is composed of 65 Silica, IS Alumina, 14 Potash, and a 

 trace of Lime and Iron,) and Mica, (which consists of 36 Silica, 31 Al- 

 umina, 8 Potash, 8 Iron, and ] Magnesia,) are also abundantly distribu- 

 ted, constituting with Quartz the rock called Chanite. Frequently the 

 Mica is replaced by Hornblende, (which does not differ very much from 

 it in chemical composition, except that it contains more lime and magne- 



