VOL. LXXI.J PHILOSOPHICAL TRANSACTIONS. 45 



clay that forms the lower part of their beds. There is not any substance so 

 coarse as gravel either in the Delta or nearer the sea than 400 miles, where a 

 rocky point, a part of the base of the neighbouring hills, projects into the 

 river : but out of the vicinity of the great rivers the soil is either red, yellow, 

 or of a deep brown. 



The annual swelling and overflowing of the Ganges appears to owe its increase 

 as much to the rain water that falls in the mountains contiguous to its source, 

 and to the sources of the great northern rivers that fall into it, as to that which 

 falls in the plains of Hindoostan ; for it rises 15-l feet out of 32, the sum total 

 of its rising, by the latter end of June: and it is well known, that the rainy 

 season does not begin in most of the flat countries till about that time. In the 

 mountains it begins early in April ; and by the latter end of that month, when 

 the rain-water has reached Bengal, the rivers begin to rise, but by very slow de- 

 grees ; for the increase is only about an inch per day for the first fortnight. It 

 then gradually augments to 2 and 3 inches before any quantity of rain falls in the 

 flat countries ; and when the rain becomes general, the increase on a medium is 

 5 -nches per day. By the latter end of July all the lower parts of Bengal, con- 

 tiguous to the Ganges and Burrampocter, are overflowed, and form an inunda- 

 tion of more than 100 miles in width ; nothing appearing but villages and trees, 

 excepting very rarely the top of an elevated spot, the artificial mound of some 

 deserted village, appearing like an island. 



The inundations in Bengal differ from those in Egypt in this particular, that 

 the Nile owes its floods entirely to the rain-water that falls in the mountains 

 near its source ; but the inundations in Bengal are as much occasioned by the rain 

 that falls there, as by the waters of the Ganges ; and as a proof of it, the lands 

 in general are overflowed to a considerable height long before the bed of the 

 river is filled. It must be remarked, that the ground adjacent to the river bank, 

 to the extent of some miles, is considerably higher than the rest of the country,* 

 and serves to separate the waters ot the inundation from those of the river till it 

 overflows. This high ground is in some seasons covered a foot or more ; but the 

 height of the inundation within varies of course according to the irregularities of 

 the ground, and is in some places 1 2 feet. Even when the inundation becomes 

 general, the river still shows itself, as well by the grass and reeds on its banks, 

 as by its rapid and muddy stream ; for the water of the inundation acquires a 

 blackish hue, by having been so long stagnant among grass and other vegetables : 

 nor does it ever lose this tinge, which is a proof of the predominancy of the 



* This property of die bank is well accounted for by Count Buffbn, who imputes it to the precipi- 

 tation of mud made by the waters of the river, when it overflows. The inundation, says he, puri- 

 fies itself as it flows over the plain ; so that the precipitation must be greatest on the parts nearest to 

 the margin of the river. — Orig. 



