CHEMISTRY OF SOIL. 23 



elements of minerals. Without a knowledge of the 

 chemical constitution of minerals, the science which 

 classifies and labels these is useless. The mineral- 

 ogist 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. He must give to the as- 

 semblage of elements which composes a mineral, 

 that name which the mineralogist bestows on the as- 

 semblage of external characters, which determines 

 the species. 



37. The mineralogy of agriculture is no more 

 than this, that the farmer be able, ever to connect 

 with a certain name, a certain chemical composition. 

 Hearing mica (which is isinglass,) named, he imme- 

 diately connects with that, the chemical properties 

 which belong to the species, as he would connect 

 with the term isinglass, the physical properties of 

 that substance; such as transparency, divisibility 

 into thin plates, which are flexible and elastic. 



38. The amount of this mineralogical knowledge 

 is very limited. Seven simple minerals compose all 

 rocks, viz : quartz, mica, felspar, hornblende, talc, 

 serpentine, carbonate of lime. Other minerals are 

 found in, but these seven compose all rocks termed 



