194 THE LURE OF THE LAND 



sidence (bottom lands, alluvial soils, lacustrine deposits, 

 etc.). 



3. Those which have been deposited as debris from 

 moving masses of ice (glacial drift). 



4. Soils formed from volcanic ashes or from ma- 

 terials moved by the wind and deposited in low places 

 or in hills or ridges. 



5. Those formed chiefly from the decay of vegetable 

 matter (tule, peat, etc.). 



The importance of a more extended notice of this 

 class of soils for analytical purposes is emphasized by 

 their large extent in the United States. 



AT/R-AT.T SOILS. 



Chiefly through the researches of Hilgard attention 

 has been called to the true character of these soils 

 which are found throughout a large part of the western 

 United States and which are known by the common 

 name of alkali. The following description of the origin 

 of these soils is compiled chiefly from Hilgard's papers 

 on this subject. Wherever the rain-fall is scanty, and 

 especially where the rains do not come at any one time 

 with sufficient force to thoroughly saturate the soil 

 and carry down through the subsoil and off through 

 the drainage waters the alkali contained therein, favor- 

 able conditions exist for the production of the alkaline 

 soil mentioned above. The peculiar characteristic of 

 this soil is the efflorescence which occurs upon its sur- 

 face and which is due to the raising of soluble salts in 

 the soil by the water rising through capillary attraction 

 and evaporating from the surface, leaving the salts as 

 an efflorescence. 



Soils which contain a large amount of alkali are 

 usually very rich in mineral plant food, and if the ex- 



