CHAPTER in 



THE ORIGIN OF ALKALI 



THE presence of alkali incrustations over the surface of 

 the soil was observed long before scientists were able to 

 account for the origin of these salts. This led to quite 

 a number of theories regarding the source of the alkali. 

 Several of the early theories have been found untenable 

 in the light of later investigation. Many of the formerly 

 obscure facts are now definitely known and there is a much 

 clearer idea of the source of the soluble salts of the soil; 

 but even today considerable difference of opinion exists 

 regarding the origin of some of these salts. More data 

 must be gathered before it will be possible to state definitely 

 why certain deposits of alkali occupy their present position 

 and maintain their present composition. It is definitely 

 known that there are a number of distinct conditions 

 promoting the accumulations of alkali in various sections. 



TABLE IV. AVERAGE COMPOSITION OF IGNEOUS ROCKS, SHALE, 

 AND SANDSTONE (PER CENT) 



