WITH AGRICULTURE AND PLANTING. 469 



nourishment of plants, a soil consisting chiefly of inor- 

 ganic particles is still more necessary, both for sustaining 

 their roots, and for receiving, retaining, and partly also 

 preparing nutrition for them ; for, according to accurate 

 observations, some inorganic substances exert an influ- 

 ence upon the decomposition of animal and vegetable re- 

 mains. These effects vary much according to differences 

 in the aggregation and chemical nature of the inorganic 

 parts ; of which circumstances, however, the different qua- 

 lities of rocks are the ultimate cause. 



Two kinds of productive soil may be distinguished 

 with regard to their origin. The soil has either originated 

 in the place in which it now is from the subjacent rock, 

 or it has been transported to the places in which it is now 

 found by some power, especially by that of water. The 

 first kind may be named untransported, the second trans- 

 ported soil. To the first kind of soil is to be referred a 

 great part of the soil which covers the summits and de- 

 clivities of mountains, and to the other, the soil which 

 fills the bottoms of valleys, as well as a great part of the 

 loose soil of extensive strata in hilly countries and plains. 

 Untransported soil is generally thinner than the trans- 

 ported ; and of the two the latter is that which most fre- 

 quently occurs in low land. The first kind of soil, the 

 untransported, is found to be more or less similar, in 

 its principal constituent parts, to the rocks from which 

 it has originated; in the other kind, the transported 

 soil, on the contrary, the parts which were originally in 

 connection, have been variously separated and mixed, by 

 the agency of the powers by which its transportation was 

 effected. 



The quantity and quality of the soil derived from 



