THE CONQUEST OF ARID AMERICA 



magnesia, sulphuric and a trifle of phosphoric acids. 

 Where, on the contrary, the rainfall is insufficient to 

 carry the soluble compounds formed in the weathering 

 of the soil-mass into the country drainage, those com- 

 pounds must of necessity remain and accumulate in the 

 soil." 



All this is perfectly comprehensible, even to the lay 

 mind. The valuable ingredients of the soil which are 

 soluble have been washed out of the land in humid re- 

 gions, like our eastern States, by the rains of centuries. 

 On the other hand, these elements have been accumu- 

 lating in the arid soil of the West during the same cen- 

 turies. They lie there now like an inexhaustible bank 

 account on which the plant-life of the future may draw 

 at will without danger of protest. The process which 

 created this rich soil goes on repeating itself recreating 

 the soil season after season. The same is true, of course, 

 in the arid and semi-arid regions of Egypt, India, China, 

 and all other localities that enjoy the inestimable bless- 

 ing of aridity. 



Professor Hilgard's conclusions are the result of pa- 

 tient investigation. They are based on more than one 

 thousand analyses of the soils of the arid and the hu- 

 mid regions of the United States of the West and the 

 East. These analyses demonstrated the following as- 

 tounding fact : That the soils of the arid regions lying 

 west of the one hundredth meridian, when compared 

 with the soils of the humid region lying east of the 

 Mississippi river, contain on the average three times as 

 much potash, six times as much magnesia, and fourteen 

 times as much lime. This is the scientific explanation 

 of the superior productiveness of the arid regions of tho 



38 



