Calcutta Delta. 



551 



systems, which call to their aid the assistance of an indefinite lapse 

 of ages, wherewith to account for the various revolutions which they 

 assume in spite of revelation, to have been the agents by which our 

 strata were produced. 



Now the operations which were instrumental in producing the strata 

 of the coal measures, are simply repeated at the mouths of the Ganges, 

 although perhaps in a more limited degree than in those bygone days, 

 when nature appears to have had more ample stores, and to have acted 

 on a grander scale. Thus we have still a broad and rapid river charged 

 with its own and with the produce of the land, pouring its turbid 

 waters into the gulf, which it discolours for a distance of sixty miles 

 from the shore. How know we then that after ages may not 

 find repeated there, effects similar to those which were produced in 

 former years during the accumulation of our secondary strata ? 



In the formation of Deltas, if within the Tropics, the strata of which 

 they are composed must necessarily be subject to the greatest possible 

 degree of variation, both in respect to their materials and thickness, 

 influenced as they are by the changing seasons, and the nature of the 

 detritus and sediments brought down. 



Thus in the season when the monsoon is raging, and the rivers 

 are full and overflowing, their force and velocity will enable them 

 to carry down the sands and silts in most abundance, and a deposit 

 of sand or sandstone of more or less coarseness is the ultimate 

 result. 



But we must remember likewise that besides the sands, the waters 

 would be charged with muddy sediments of finer and lighter particles 

 both in suspension and solution, which, when the monsoon abated and 

 the waters became more tranquil, would be deposited in a clayey stra- 

 tum above the sands, whose greater specific gravity had caused them 

 to sink first. 



Nor is this a mere vague hypothesis put forth at random in sup- 

 port of a preconceived theory, but is based on the results of Mr. Ever- 

 est's experiments on the quantity of earthy matter brought down by 

 the Ganges river. Our whole data therefore stands thus :— 



Season. 



Rains, 



Winter, 



Hot weather, 



4 months, 



5 months, 

 3 months, 



Velocity ft. 

 per hour. 



494,208 

 71,200 

 36,330 



Cubic feet 

 discharged 

 per second. 



23,800 

 7,435 

 4,445 



34 grains per wine quart was found to be the average for the rains. 



