GEOLOGY OF SOIL. 21 



has been a universal mingling of the loose material, 

 soil, derived from worn down and mingled rocks. 



32. The same uniformity of chemical composi- 

 tion characterizes soil, which characterized rocks ; 

 that is, great similarity, but not identity, and it is on 

 limited patches only, that soil partakes decidedly of 

 the character of the underlaying rocks. 



33. The extensive analyses of soil, executed by 

 the geological surveyor of Massachusetts, taken from 

 every variety of rock formation, present a remarka- 

 ble uniformity, both of chemical constitution, and 

 mineralogical composition of the earthy ingredients. 

 The same truth is presented by the analysis of soil 

 from various parts of the globe. It is a conclusion, 

 warranted by the widest examination, that the min- 

 eral constituents of 100 parts of the soil of our globe, 

 is composed of sand or silicates 89 # 28 ; salts of lime 

 00-85. — The terms salts, and silicates, will be ex- 

 plained in the next chapter. 



