22 THE ORIGIN OF ALKALI 



is the predominating base in the readily soluble salts at 

 the surface." 



This hypothesis does not explain the method of accumu- 

 lation of alkali at certain places in the soil; it merely 

 attempts to show why certain salts are present at the sur- 

 face in larger quantities than others. 



Salts from Ancient Seas. The observation that alkali 

 is found in large quantities in one section, whereas it 

 may be almost entirely lacking in another section of sim- 

 ilar climatic conditions early led to an attempt to trace 

 the salt to the rock from which the soil was formed. 

 Traphagen (21), at the suggestion of W. H. Weed of the 

 U. S. Geological Survey, made a comparison of the composi- 

 tion of the alkali near Billings, Montana, with the soluble 

 salts in the Fort Benton shales from which the soils were 

 in part derived. As a result of this study he was led to 

 the conclusion that in this case the soluble salts in the soil 

 resulted from a transference of the salts to the soil while 

 the shale was being disintegrated. This theory was 

 afterward supported by the work of Whitney and Means 

 (23) in the same region. Cameron (4) also mentions shale 

 and similar deposits as a source of alkalies. 



It seems, however, to have been left for Stewart, Peter- 

 son, and Greaves (17, 16, 19, 18) to explain clearly the 

 intimate relation existing between present alkali accu- 

 mulations and the presence of large quantities of alkali 

 salts in country rocks from which these soils were formed. 

 They made extensive examinations of the geological 

 formations in Utah, Colorado, Arizona, Wyoming, Idaho, 

 and Nevada, and analyzed the soil-forming country rock 

 of these areas. 



These examinations and analyses revealed the fact that 

 in these sections wherever alkali is present in very large 



