546 Remarks on the 



although now overlaid throughout a great extent by the alluvium which 

 the numerous rivers have swept down from the higher lands, and dis- 

 posed above it. 



If this be true, it will be at once apparent that the fall of the rivers 

 from the present mountains towards the sea would have been far greater 

 before the deposition of such alluvium than now, for the accumulation 

 of strata, by gradually filling up the slope and forming more level lands, 

 would tend materially to check the velocity and power of transport, 

 until it became reduced to what we find it in the present time. 



If, on the other hand, and as in the absence of more positive data, 

 I am inclined to think most probable, the Delta conglomerate was 

 formed of fragments torn from the uprising primary rocks in various 

 parts of India, at the time when the deluge was subsiding, — that con- 

 glomerate will have been deposited by the retiring waters of the ocean, 

 when it was forced back by the uprise of the land; and in it, and probably 

 in strata deposited immediately upon it, may be imbedded also some 

 traces of the fossils and detritus of the true diluvium, brought down by 

 the waves which washed over it as it first emerged to clay, and also by 

 the present rivers, which then first began to flow towards the sea. 



To the same causes may also probably be referred the distribution of 

 the Nerbudda, Jumna, and Irawaddi fossils, and thus while the inclined 

 strata of the sub-Himalayan range, represent truly the diluvial beds, 

 which were accumulated during the rise and prevalence of the deluge, the 

 dispersed fossils of the other localities may be referred, in accordance with 

 Dr. Buckland's opinion, to a " more modern" period, namely, to the sub- 

 siding of that deluge, which in its retirement from the land, dispersed 

 them abroad, by its cui'rents, from the places where they had been ori- 

 ginally deposited. These then, in contradistinction to the stratified 

 beds of the true diluvium, may be properly termed, diluvial detritus. 



With regard to the lapse of time required to form a given portion of 

 the Gangetic Delta, we are, I conceive, altogether left without any cer- 

 tain data ; for so much must always depend upon the depth to be filled 

 up, and the quantity of detritus brought down, that the periods would 

 vary greatly in duration. 



Thus the failure or mildness of the Monsoon for several, or even for 

 a few, seasons, would materially retard the formation of new land, by 

 limiting the supplies of transported matter ; while afterwards, in a pe- 

 riod of equal duration, but in which the rains had been heavy, and 

 detritus abundant, a larger share of deposits would be recovered from 

 the sea. If now during both these terms, observations should be made 



