Chap. 13.] w. blanford, westeen india. 75 



valleys {a) . This appears d\ie to the more argillaceous portions of the dis- 

 integrated basalts being washed away from the slopes and deposited in 

 the valley^ forming a soil much more retentive of moisture and conse- 

 quently more marshy and more impregnated with organic matter {b) . Of 

 course agricultural processes tend to change the surface and to obscure 

 the history of these deposits. 



The abrupt termination of the regur at the edge of the traps is 



simply due to a change from an argillaceous soil 

 Cause of boundary of 

 cotton soil and of traps to a Sandy one. The traps appear almost always 

 "being identical. i • i i i • 



to decompose into a highly aluminous substance ; 



the metamorphic rocks, on the other hand, yield sand to a large extent, 

 while the finer kaolin produced by the disintegration of their felspar is, 

 to a great extent, washed away by rain, leaving an excess of quartz 

 sand in the soil. Where this kaolin is redeposited as clay, there is often 

 a surface of regur as in Southern India. 



These views will probably reconcile all the difficulties concerning the 

 distribution of regur. 



(a). This has been pointed out by Mr. Dalzell in a communication published in one of 

 the Bombay newspapers. 



(6). An instance outside of the area now described may be here mentioned to shew the 

 effect of retention of moisture and marshy condition in blackening the soil. About 3 miles 

 south of Poona, near the Parsee Towers of Silence, are several rises, upon which two terraces, 

 formed of different beds of trap, are conspicuous. The uppermost of these terraces 

 evidently consists of a less pervious stratum than the lower one — the vegetation upon it is 

 rank, abounding in a species of Carex and other marsh loving plants. Upon this terrace 

 the soil is black ; upon the other, which is much drier, it is a reddish brown. 



(237 ) 



