212 MOVEMENTS OF SALTS IN THE SOIL 



vary with the other associated conditions. In the great 

 Californian valley, with a rainfall varying in different parts 

 between 34 and 6 inches, alkali lands are met with only where 

 the rainfall is below 20 inches. In the North- West Provinces 

 of India, alkali lands are found with a rainfall as high as 24-28 

 inches. The rain in these two localities is however very 

 differently distributed. In California the rain nearly all 

 occurs between November and April; it falls thus in the 

 cooler portion of the year, when least is lost by evaporation ; 

 its whole effect is also concentrated into a few months. Under 

 these circumstances the rain produces the greatest amount of 

 percolation through the soil which is possible under the cir- 

 cumstances. In India, on the other hand, half the rain falls 

 as a torrent in July and August, the greater part of which 

 runs off the surface instead of penetrating the soil ; while 

 the remainder of the rainfall is distributed throughout the 

 rest of the year. The same amount of rain thus produces 

 a smaller amount of percolation in the Indian than in the 

 Californian climate. 



The texture of the soil has also a considerable influence 

 on the production of alkali land. In a coarse-grained soil, 

 having little power of retaining water, a considerable amount 

 of percolation may occur even with a small rainfall ; in such 

 a soil there will also be little return of saline solutions to 

 the surface by capillary action. In a soil composed of fine 

 particles both conditions are reversed. Percolation is here 

 diminished ; the rise of salt solutions to the surface by 

 capillary action in dry weather also becomes more con- 

 siderable; the conditions are thus far more favourable for 

 the accumulation of saline matter in the surface soil. The 

 occurrence of a pan in the subsoil, preventing or hindering 



