CHAPTER II. 



CHEMICAL CONSTITUTION OF ROCKS, AND SOIL. 



34. The geologist, the mineralogist, the chemist, each 

 views rocks with a different eye. The geologist regards 

 the rocky mass; the mineralogist, the simple minerals corn- 

 posing the rock ; the chemist, the simple elements which 

 compose the minerals. 



35. Elements are substances which have not as yet been 

 proved to be compound, as oxygen and hydrogen among the 

 gases, or iron or lead among metals. Minerals are called 

 simple which have certain definite, external, physical char- 

 acters, though they may be composed of several elements. 

 Rocks are called compound, which consist of several simple 

 minerals, as granite, which consists of quartz, felspar, and 

 mica. 



36. The only point of view which the farmer takes, is 

 that of the chemist ; his pole-star is '* fruit and progress ;" 

 and his philosophy, guided by this, teaches the nature and 

 mode of action of the several elements of minerals. With- 

 out a knowledge of the chemical constitution of minerals, 

 the science which classifies and labels these is useless. The 

 mineralogist merely names his mineral, labels it, and places 

 it in his cabinet ; yet a farmer must know a few of these 

 names, and talk to the mineralogist in terms which he can 

 understand. lie must give to the assemblage of elements 

 which composes a mineral, that name which the mineralo- 



