GEOLOGY. CHEMISTRY. THE EOCKS. 75 



fallen, from the sky. These are often found upon or near 

 the surface, and consisting of iron and two other pure 

 metals not oxidized, in the form of a brilliant, malleable 

 compound. All the rest, whether found at the surface 

 or deep beneath, are in rocks or the fragments of rocks. 



265. The study which searches into the structure of 

 the earth, asks what the rocks are and in what order they 

 lie, and examines the curious remains of plants and of 

 animals that are often found in them, is geology ; and a 

 person who pursues this study is a geologist. 



The study which searches into the inner nature of 

 things, to find out what they are, what they are made of, 

 and how they act on each other and on animals and 

 plants, is chemistry. A person who pursues this study, 

 with experiments, is a chemist ; and the process of search 

 ing, by experiments, and separating a compound sub 

 stance into its elements, is chemical analysis. 



266. The Soil is that part of the ground which can be 

 tilled, which can be reached and stirred by agricultural 

 tools. It is made up of many different kinds of earth. Of 

 these the three most important are silicious earth or sand, 

 argillaceous earth or clay, and calcareous earth or that 

 made of limestone or carbonate of lime ; and, by the 

 mixture of these three, most of the different kinds of soil 

 are formed. 



267. The soil which covers the surface of the earth 

 rests upon rocks lying at a greater or less depth beneath, 

 from the crumbling or disintegration of which the soil 

 and loose earth have apparently been formed. 



The principal and most important of these rocks are 

 the following : first, Granitic Rocks, including Greenstone 

 Rocks ; second, Silicious Rocks ; third, Slaty or Argilla- 



