134 GEOLOGY OF TRICIIINOPOLY,, &C. [ClIAP. VI. 



The fine black soil just on the surfaces of the peat bogs and drying-- 



Black soil of the Nil- ^P swamps at the bases of many '^sholahs'' 



^^""^^' (woods) on the Nilghiris, is undoubtedly formed in 



the same manner. In the dense damp forests of the Anamullays, south 



of Coimbatoor, the black soil is still a highly vege- 

 of the Anamullays. , • , t, i i • 



table one, owing to so little exposure to weathering 



influences. 



In tank beds and jheels of India generally, there is possibly more 



of animal life going on ; but there is at the same 



Mud of tanks, &c. , . . , „, . , , n t-n , • i -i i 



time quite suflicient vegetable me to yield the 



amount of vegetable organic matter necessary for the production of this 

 soil, and, above all, these localities are exposed to atmospheric influences far 

 more powerful than is the case with the peat of Ireland, or of the Nil- 

 Atmospheric influences g^^'is. It is the intensification of the weathering 

 instrumental. influences of the Indian climate which appears to 



us to be the great agent in the production of this soil, and which 

 accounts in great measure for the almost total destruction and consequent 

 absence of all organic remains in recent deposits where we know that 

 life has been so largely developed. 



We have seen numerous instances of back-water mud which is now 



Back-water deposits dry land, and which has not turned to Cotton-soil, 

 not generally productive 

 of regur. and this is in all probability owing to vegetable life 



having been so sparingly developed in it. Should the back-water area 

 become subject to fresh water inundations, there would then be an oppor- 

 tunity for the development of vegetation to a sufficient extent, and this 

 has probably been the case with the Mercanum area referred to by Mr. 

 Blanford in his Memoir on the Cretaceous Rocks of Southern India. The 

 Mercanum back-water. Mercanum area was once a back-water, but is now, 

 essentially fresh water. jf ^^ ^^.^ ^^^ mistaken, cut off from the sea by 



a permanent bar, and periodically inundated by fresh water. It is along 

 { 356 ) 



