28 THE ORIGIN OF ALKALI 



the coast of Southern California derived their soluble 

 salts from ocean water, which was inclosed in arms shut 

 off from the main body of the ocean. 



Evaporation of Saline Lakes. In arid countries nu- 

 merous lakes without an outlet to the sea are found. All 

 the water running into them is evaporated leaving the 

 dissolved material to be gradually concentrated until the 

 waters become saturated. Around the bodies of these 

 lakes the soil is likely to be high in soluble salts. Arms of 

 the lake may be shut off in the manner already described. 

 These become centers of local salt accumulation. The 

 lands for some distance surrounding these saline lakes are 

 likely to be somewhat impregnated with alkali, but as the 

 water is approached the concentration is generally in- 

 creased. There is usually a fringe near the lake that is 

 entirely unproductive. This is surrounded by a zone in 

 which only alkali-resistant plants grow, and still farther 

 away the less-resistant plants are found. The Great Salt 

 Lake in Utah is an example of this kind. 



Formation of Soluble Carbonates. On account of their 

 soluble action on the organic matter of the soil and the 

 hard crust which they form on the soil, the soluble car- 

 bonates are, of all the soluble salts, most to be dreaded. 

 Fortunately, they are not so widespread in their occurrence 

 as are the chlorides and sulphates. The comparatively 

 insoluble carbonates of calcium and magnesium are very 

 abundant but, being only slightly soluble, they are seldom 

 if ever harmful to plants. 



The exact method of soluble-carbonate formation is not 

 well known. Cameron (3), from studies of greasewood 

 and the creosote bush, held that these plants are instru- 

 mental in converting the neutral salts into carbonates. 

 Aladjem (i), from laboratory experiments with soil kept 



