64 GEOLOGY OF AGRICULTUEE. 



a primary region, as large portions of Massachusetts ; 

 if above secondary rocks, a secondary region ; if above 

 tertiary rocks, tertiary ; and if above alluvial deposits^ 

 alluvial^ thus naming each district from the underlay- 

 ing formation. 



99. Let us now look at some of the changes which 

 the soil must have undergone. No one can examine 

 it with a powerful microscope without perceiving that 

 it consists principally of rock broken down to various 

 degrees of fineness, from the troublesome boulder to 

 the minutest particle. It bears unmistakable marks 

 of an igneous origin. It must have been once belched 

 from the bosom of the earth in a state of intense igni- 

 tion. From this state it must have been cooled and 

 solidified. Much of it also bears indubitable marks 

 of having been since broken up, violently agitated by 

 water, and again solidified in the form of stratified 

 rock. From this state it appears to have been again 

 broken up and distributed about the earth in the form 

 of boulders, pebbles, hoarse sand, fine sand, and clay. 

 The action of rains and frost has been long at work, 

 rendering it still finer than when first deposited in its 

 present locations. If we could go back to a time 

 when the earth was, in the language of Scripture, 

 *' without form and void," or, as it might be trans- 

 lated, " was desolation and emptiness," when as yet 

 no plants had sprung from its surface, we should 

 probably find the materials which now constitute our 

 soils in a comparatively coarse and upcultivable 

 state. In process of time shrubs and trees ' -prung up. 

 Successive growths lived and perished, d] ,*ying their 



