480 



ANTIQUITY OF THE DELTA. 



[Ch. XIX. 



At the depth of about 400 feet below the surface, an abrupt 

 change was observed in the character of the strata, which 

 were composed in great part of sand, shingle, and boulders 

 the only fossils observed being the vertebra of a crocodile, 

 shell of a trionyx, and fragments of wood very little altered 

 and similar to that buried in beds far above. These gravelly 

 beds constituted the bottom of the section at the depth of 481 

 feet, when the operations were discontinued in consequence 

 of an accident which happened to the auger. 



The occurrence of pebbles at the depths of 120 and 400 feet 

 implies an important change in the geographical condition of 

 the region around or near Calcutta. The fall of the river, or 

 the general slope of the alluvial plain, may have been for- 

 merly greater ; or, before a general and perhaps unequal sub- 

 sidence, hills once nearer the present base of the delta may 

 have risen several hundred feet, forming islands in the bay, 

 which may have sunk gradually, and become buried under 

 fluviatile sediment. 



i 



matter 



scientific interest, if experiments were made to enable us to 

 determine, with some degree of accuracy, the mean quantity 

 of earthy matter discharged annually into the sea by the 

 united waters of the Ganges and Brahmapootra. The Rev. 

 Mr. Everest instituted, in 1831-2, a series of observations on 



poor 



rthy matter brought down b 

 500 miles from the sea. He 



number 



second at that place was during the 



Rains (4 months) 

 Winter (5 months) . 

 Hot weather (3 months) . 



494,208 

 71,200 

 36,330 



so that we may state in round numbers that 500,000 cubic 

 feet per second flow down during the four months of the flood 

 season, from June to September, and about 55,000 per second 

 during the remaining eight months. 



The average quantity of solid matter suspended in the water 

 during the rains was, by weight, ^th part ; but as the water 

 is about one half the specific gravity of the dried mud, the 

 solid matter discharged is -^th part in bulk, or 577 cubic 







J aim' 











15 



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