GEOLOGY OF AGRICULTURE. 63 



ORIGIN OP SOILS. 



83. All soils, Avbether alluvial, drift, or tertiary in 

 their origin, are derived from roclcs, broken down, 

 ground to a greater or less degree of fineness, and so 

 disseminated that the ruins of one rock may be sup- 

 posed to be mixed, in most cases, with those of a great 

 many others. | The idea that soil§, have originated 

 from the rock immediately under them is an error. 

 When the drift period was, is not known, except that 

 it was subsequent to fhe tertiary and anterior to" the 

 historic period ; nor is it known what the drift agency 

 was ; but it is known, as well as anything can be, that 

 some tremendous power was at work tearing up, trans- 

 porting, and mixing the loose materials on the earth's 

 surface. The soil on nearly every foot of land in our 

 country — and the same is true of Europe, at least, if 

 not of the whole world — has come from many and 

 wide-spread localities. I Every soil may be considered 

 as a mixture of many soils. If every particle in a 

 cubic foot of earth were to be endowed with instinct, 

 and were to rise up and take its departure for its ori- 

 ginal rocky home, I have no doubt there would be a 

 wide scattering, and I believe an extent of travel would 

 be shown quite surprising to those who have not re- 

 flected on the subject. 



84. If these views are correct — if the loose materials 

 on the earth's surface have been extensively trans- 

 ported, scattered, and mixed — if they are now so min- 

 gled and confounded that the acutest geologist can de- 

 tect the origin of only the coarser parts (boulders, 



