42 PHILOSOPHICAL TRANSACTIONS. [ANNO 1781. 



deep water near it: and on the opposite side a bank, shelving away so gradually 

 as to occasion shallow water at some distance from the margin. This is more 

 particularly the case in the most winding parts of the river, because the very 

 operation of winding produces the steep and shelving banks: for the current is 

 always strongest on the external side of the curve formed by the serpentine 

 course of the river; and its continual action on the banks either undermines 

 them, or washes them down. In places where the current is remarkably rapid, 

 or the soil uncommonly loose, such tracts of land are swept away in the course 

 of one season, as would astonish those who have not been eye-witnesses to the 

 magnitude and force of the mighty streams occasioned by the periodical rains of 

 the tropical regions. This necessarily produces a gradual change in the course 

 of the river; what is lost on one side being gained on the other, by the mere 

 operation of the stream: for the fallen pieces of the bank dissolve quickly into 

 muddy sand, which is hurried away by the current along the border of the 

 channel to the point whence the river turns off to form the next reach, where 

 the stream becoming weak, it finds a resting place, and helps to form a shelving- 

 bank, which commences at the point, and extends downwards, along the side 

 of the succeeding reach. 



It is evident that the repeated additions made to the shelving bank above- 

 mentioned, become in time an encroachment on the channel of the river; and 

 this is again counterbalanced by the depredations made on the opposite steep 

 bank, the fragments of which, either bring about a repetition of the circum- 

 stances above recited, or form a bank or shallow in the midst of the channel. 

 Thus a steep and a shelving bank are alternately formed in the crooked parts of 

 the river (the steep one being the indented side, and the shelving one the pro- 

 jecting) ; and thus a continual fluctuation of course is induced in all the wind- 

 ing parts of the river ; each meander having a perpetual tendency to deviate 

 more and more from the line of the general course of the river, by eating deeper 

 in the bays, and at the same time adding to the points, till either the opposite 

 bays meet, or the stream breaks through the narrow isthmus, and restores a 

 temporary straightness to the channel. 



Several of the windings of the Ganges and its branches are fast approaching 

 to this state ; and in others, it actually exists at present. The experience of 

 these changes should operate against attempting canals of any length, in the 

 higher parts of the country ; and I much doubt, if any in the lower parts would 

 long continue navigable. During 1 1 years of my residence in Bengal, the out- 

 let or head of the Jellinghy river was gradually removed 4 of a mile farther 

 down : and by 2 surveys of a part of the adjacent bank of the Ganges, taken 

 about the distance of Q years from each other, it appeared that the breadth of an 

 English mile and a half had been taken away. This is however the most rapid 



