322 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [Apr. 1, 



I. General Considerations. 

 1. Introduction. — It may seem presumptuous in one who is neither 

 a geologist nor has any pretension to geological knowledge to ven- 

 ture to address this Society on a subject so nearly akin to their 

 special science. My excuse must be that, having resided for five 

 years on the banks of one of the most active of the Bengal rivers, I 

 have had opjDortunities which are not vouchsafed to every one of 

 observing their phenomena, and have been a witness of the changes 

 I am about to describe. I may also, perhaps, be allowed to state that, 

 when I first became aware of the disturbance that was taking place 

 around me, I set myself carefully to measure and observe what was 

 passing ; and, in 1835, made a sketch-survey of the lower Ganges 

 and Brahmapootra, from Jaffiergunge to the sea. This was published 

 by Mr.Tassin a few years afterwards, and is, so far as I know, the only 

 survey that was made — certainly the only one published — between 

 that made by Major Rennell and the survey now in progress, but 

 which has not yet been given to the world. I may also mention, in 

 extenuation, that I have waited for more than a quarter of a century 

 in order that some one more worthy might undertake the task ; but, 

 as no one has come forward, I may perhaps be now excused for 

 venturing upon it. 



In order, however, to obviate the reproach of presumption, my 

 intention is to confine myself wholly to the historical period, and 

 practically to the time that elapsed between the survey made by the 

 celebrated Major Eennell, between the years 1780-90, and the survey 

 now in progress ; and though I shall be obliged, occasionally, to 

 mention facts that may have occurred before the Christian era, they 

 will be only such as are based on human evidence, and not such as 

 properly fall within the domain of the geologist. 



2. Oscillation of Rivers. — Before describing the actual phenomena, 

 it may be necessary to call attention to certain principles — not very 

 recondite, perhaps, but indispensable to a clear understanding of 

 what is to follow. 



The first of these is : — 



All rivers oscillate in curves, whose extent is directly propor- 

 tionate to the quantity of water flowing through the rivers. 



An inspection of any good map is sufficient to prove the general 

 correctness of this dictum, but its consequences have been strangely 

 overlooked both by engineers and potamologists. Without attempting 

 to enter into the theory of the question, it may be sufficient for the 

 present to state, in illustration, that the action of rivers appears to 

 be the exact converse of that of the pendulum. 



The pendulum is a body in stable equilibrium, whose natural con- 

 dition is consequently that of rest, and, being once disturbed, it seeks 

 to regain that position ; but, the original force remaining, it would 

 go on oscillating for ever if we could abstract all the natural con- 

 ditions of friction, resistance of the atmosphere, &c. 



A river, on the contrary, is a body of water in unstable equili- 

 brium, whose normal condition is that of motion down an inclined 

 plane ; and, if we could in like manner abstract all the natural 



