MUCK M^NUA.L, 



CHAPTER I. 



GEOLOGY OF SOIL. 



1. Agricultural chemistry aims to explain all the actions 

 of earth, air, and water, upon plants. It refers to all their 

 chemical relations, to the geology, mineralogy and chem- 

 istry of soil. 



2. Agricultural geology explains the relations which soil 

 bears to plants, and the manner in which that affects vege- 

 tation. 



3. Agricultural geology confines itself to facts. It digs 

 into the earth, observes what composes that. Conversant 

 only with facts, or logical deductions from these, it leaves 

 to geology proper, the vast mass of observations, supported 

 by the highest modern science, which teaches the origin, 

 mode of formation, original condition of our globe, and the 

 successive changes which it has undergone. 



4. The terms, primary and secondary, used by geologists, 

 are almost parts of common language, — yet need to be ex- 

 plained to the farmer. 



5. Large tracts of all extensive countries are composed 

 of rocks of a granitic texture. This needs no definition. 

 Such rocks having been observed to underlay all others, in 

 the scale of rocks composing the earth's crust, were called 

 primary. It was supposed that these were first formed. 

 Out of the ruins of these, no matter when or how ruined, 



(17) 



