22 



SOILS. 



INFLUENCE OF RAINFALL ON SOIL FORMATION ; LEACHING OF 



THE LAND. 



In the general consideration of the soil-forming processes, 

 it has been stated that soils formed by the disintegration of 

 rocks " in place," i. e., without removal from the original 

 locality, are also designated as " residual "; meaning thereby 

 that only a portion of the original rock remains to form the 

 soil mass, while another portion has been removed. To a slight 

 extent this removal occurs by the partial washing-away of the 

 finest clay and silt particles; but the most important action 

 from the agricultural point of view is the removal by leaching 

 with the carbonated water of the atmosphere and soil, of cer- 

 tain easily-soluble compounds formed in the process of chemical 

 decomposition of rocks and resultant soils. The nature of these 

 compounds is exemplified in the subjoined table giving the 

 composition of some waters flowing from drains in unmanured 

 fields, laid at depths of from two to three feet ; and for compari- 

 son with these, the composition of the water of some of the 

 world's large rivers, showing what these largest drains carry 

 into the ocean. 



The analyses have in all cases, where necessary, been re- 

 calculated to parts per million, and to oxids, from the published 

 data. 



The letter " c " indicates that the preceding figure has in the 

 absence of a direct determination been stoichiometrically cal- 

 culated from the data given, in order to complete the com- 

 parison. 



COMPOSITION OF DRAINAGE WATERS FROM UNMANTRED GROUND. 



PARTS PER MILLION. 



