WITH AGRICULTURE AND PLANTING. 481 



vered with a clayey soil, which has not been produced 

 by the decomposition of the principal strata themselves, 

 but by that of the slate- clay and argillaceous marl alter- 

 nating with them. 



Hitherto we have considered untransported soil, or that 

 produced from the disintegration or decomposition of the 

 subjacent rocks in the places where it occurs ; we have 

 now to examine the relations which exist between the 

 subjacent rock, and the transported soil lying upon it. 

 The nature of the rock does not indeed influence, except- 

 ing in a more remote degree, the transported soil, which 

 has been carried to a greater or less distance from the 

 places of [its production, by the agency of moving 

 powers, and again deposited of various forms and 

 compositions. However, it may often be plainly seen, 

 that the materials of this soil have been derived from 

 particular rocks, and that these rocks have exerted some 

 degree of influence over the formation and distribution 

 of the transported soil. The examination of these rela- 

 tions is of great importance, because it is with secondary 

 or transported soil that agriculture is principally con- 

 cerned. The varieties of transported soil depend chiefly 

 upon three circumstances : \st 9 The nature of the rocks 

 from which they are derived ; 2c%, The quality and ef- 

 fect of the moving powers ; &%, The changes which they 

 may have undergone after their formation. 



The origin of the materials which enter into the com- 

 position of transported soil, has been already considered. 

 From their difference may be easily explained why soil 

 generated from the debris of primitive crystalline rocks 

 has different qualities from soil which has been derived 

 from strata of sandstone or marl. 



Hh 



