FARM AND SCHOOL PROBLEMS. 



the smallest fissures ; the water congeals and by expansion enlarge: 

 the fissures or bursts the rocks into fragments. 



So by studying the composition of rocks we can determin< 

 which are most easily disintegrated and by a study of soils w< 

 can determine from what kind of rocks they have come. Thi; 

 study of rocks and their composition has been of great importance 

 to agriculture. Lime, phosphorus and potassium, three of th< 

 elements most important to ag- 

 riculture are taken chiefly from 

 rocks. 



According to geologists 

 there have been many forces at 



FIG. 1. How the Soils were formed. 



FIG. 2. Formations. Soils, Lakes 

 and Mountains. 



work that have in many ways been responsible for the variatioi 

 that now exists in our soils, and that have resulted in many of th< 

 diversifications of agriculture. 



In the formation of the earth's crust many of the element 

 necessary to plant and animal life were combined in the formatioi 

 of various rocks. The mountains were the first parts of th 

 earth's crust to appear above the waters of a shallow ocean 

 This has been accounted for through the theory of the contrac 



