416 SOILS. 



under any definite category either from the chemical or physical 

 point of view, except as to their red tint. Even this tint, how- 

 ever, is not always found associated with exceptionally high 

 contents of iron oxid, but due rather to its fine diffusion in the 

 soil mass. As compared with the regur, with which the 

 " red " areas are interspersed, these soils contain, on the aver- 

 age, less lime, potash and ferric oxid; and phosphoric acid is 

 uniformly low. The alluvial (brown and black) soils from 

 the same region, exemplified in the table, are doubtless derived 

 partly from the regur, and their color and composition varies 

 accordingly. 



" Laterite Soils." These are defined by Wohltmann ( Trop- 

 ische Agricultur, 1892) as being " the characteristic sedentary 

 soils (Verwitterungsboden) of the tropics, formed under the 

 influence of heavy precipitation, high temperatures and 

 drought." This definition does not indicate their derivation 

 from any particular rock, such as laterite is supposed to be ; but 

 its definition puzzles even geologists, and so, as Leather ob- 

 serves, the definition of laterite soils will naturally puzzle 

 agricultural chemists. Accordingly it is difficult to deduce 

 from the analyses given any definite common characters. 

 Leather describes those analyzed by him as red or reddish, 

 sandy and gravelly, the gravel or cobbles often incrusted with 

 a dark-smooth crust of limonite, which to the uninitiated looks 

 as though the rock itself had been fused and vitrified. The 

 samples from Lohardaga and Singhbhum show the effects of 

 these limonite crusts upon the composition of the soils, which 

 resembles that of the Hawaiian soils mentioned above ; but in 

 the latter the iron oxid is wholly pulverulent. But it is prob- 

 able that, as in the case of the latter, the high content of 

 phosphoric acid shown in the statement ( .64 for the Lohardaga 

 soil) is tightly locked up in the insoluble form of ferric phos- 

 phate. Wohltmann's definition of laterite soils seems best rep- 

 resented by the " terra roxa " of Brazil, which as he states has 

 .02 to .08% of potash. .02 to .10% of lime, and .045 to 

 .10% of phosphoric acid. Humus and nitrogen are very de- 

 ficient in all these soils. 



While most prominent in the coast region of Bengal, they 

 also occur not only near Madras (Saidapet) but also in the 



