RELATION TO FERTILITY 19 



analysis shows it to contain a good deal more clay than No. i. 

 Hilgard points out, however, that the heaviness of a soil is 

 largely determined by the sum of the three finest constituents, 

 the influence of which is further modified by the presence of 

 coarse sand, lime, and ferric oxide. In the present soil 106 

 per cent, of ferric oxide, and 0-8 per cent, of lime were present, 

 with some sand ; the effect of these constituents was to reduce 

 the tenacity of the clay. 



The loam subsoil which stands next in the table represents 

 a first-class upland cotton soil. It is pretty easily tilled, but 

 suffers much from swelling in alternate frost and thaw, and 

 from denudation during heavy rain, owing to its being not 

 sufficiently pervious to water. The proportion of clay is here 

 considerably reduced, but the soil is composed almost entirely 

 of the finer constituents. 



The sandy loam soil and subsoil belong to the drift period ; 

 they are characterized by the growth of the long-leaved pine. 

 The soil is very light and easily tilled. We have come now 

 to soils containing much less clay, and a considerable pro- 

 portion of coarse sand. It will be remarked that the coarser 

 constituents preponderate in the surface soil, and the finer 

 constituents in the subsoil. This is a general fact in all soils 

 from districts having a considerable rainfall; in the arid 

 regions of the United States this difference is not observed. 

 The preponderance of coarser particles in the surface soil is 

 due to the gradual removal of the finest particles from the 

 surface by rain water. Further illustrations on this point 

 will be found on pp. 45-9. 



The river deposit is a light, very porous soil, of great 

 fertility, recently deposited by the Mississippi. It is largely 

 composed of silt and very fine sand, the principal portion of 



C 2 



