Cjiap. VI.] 



SUPERFICIAL DEPOSITS AND SOILS. 



133 



■ According to existing chemical analysis, there is very little organic 

 tiiatter in this soil^ the mean result of observations being about four per 

 cent. " M. D'Archiac quotes the following analysis in his Ilistoire des 

 progres de la Geologie" (Vol. II, page 329), but without stating from 

 what part of India the sample in question was derived : — 



Silica .... 48-a 



Alumina ... ... 



Carbonate of lime ... 



„ of magnesia 

 Oxide of Iron 

 Water and organic matter 



20-3 



lG-0 



10-3 



1-0 



4-3 



100-0 



In appearance the Cotton-soil bears a strong resemblance to the 



Eesemblance to otlier ^^^ck soil of the 1^ ilghiris, of the AnamuUay forests, 



^° ^* and of the ' bottoms' and parts of the surfaces of 



peat bogs in Ireland. It is also very like in appearance, and probably of 



similar origin, to the black mud soils at present forming on the beds of 



most tanks and jheels and of some of the back-waters of India. 



Looking at the Cotton-soil, then, as compared with these soils, we are 

 inclined to regard it as a sedimentary deposit mixed with organic matter, 

 chiefly vegetable in its origin, and we further believe the deposits to have 

 been formed more generally in fresh than in brackish waters.'^ 



The black soil, or ' Maiden earth,' which is formed on the surfaces 



Maiden earth of peat ^f peat bogs in Ireland, contains very little organic 



°^' matter, and is derived from the peat through the 



exposure of that deposit to atmospheric influences, when the organic 



matter is decomposed by the liberation of the carbonic acid. 



* Mr. Henry F. Blanford lias already put forward the idea of this soil being mainly 

 of Lagoon origin. 



( 355 ) 



