1863.] FERGUSS0N DELTA OF THE GANGES. 331 



the hills by the greater energy of the northern streams, and the mass 

 of their accumulations, the only southern stream of sufficient power 

 to keep it off its hills being the Soane. 



The Brahmapootra still maintains itself nearly in the centre of its 

 valley for the greater part of its course, but it must be pushed south- 

 wards, as the Ganges has been, in the exact ratio in which the 

 quantity of water flowing from the Himalayas exceeds that draining 

 from the southern hills ; and, as this takes place, the valley must 

 rapidly be filled up and become habitable, which it hardly can now 

 be said to be in most parts. 



Though it is dangerous to descend to particulars in such matters, 

 my impression is that hardly more than 4000 or 5000 years have 

 elapsed since the sea, or rather the tide, was at or near Rajmahal ; or, 

 to speak more correctly, since the greater part of the province of 

 Bengal Proper was a great lagoon, like those which exist at the 

 mouths of the Brenta or the Po, or the Lakes Mensaleh and Boorlos, 

 at the mouths of the Nile : for there is no reason to suppose that there 

 did not always exist — in historical times at least — a bar or barrier 

 where the tides turned somewhere very near where the Sunderbuns 

 now are ; but between this and the apex of the Delta all seems to 

 have been a tidal swamp. When this was the case, the upper valley 

 of the Ganges was in the semi-habitable state in which we now find 

 Assam ; and I fancy we can, in history, trace the settlements that 

 were made one after another, proceeding eastward as the Delta ex- 

 tended, and, by its elevation, diminished the slope of the bed of the 

 Ganges to what we now find it. 



2. The Silting-up of the Sylhet Jheels. — To return, however, to 

 the Sylhet Jheels. When the Brahmapootra was first turned into 

 them, they consisted of an immense tract of submerged country, 

 covered with clean still water of no great depth, and consequently 

 every particle of silt that was brought into them was seized upon 

 and deposited; and the Luckia and Megna, which flowed out of 

 them, must then have been, as they are now, clear and pellucid 

 streams, as compared with the turbid waters of the two great rivers. 



The first effect of this invasion, that we trace on the map, is that 

 the Soorma and other streams which flowed from Munnipore due 

 westward, along the foot of the Cossya Mountains, were deflected 

 southwards, which it was easy enough for the great river to do, so 

 long as it could take them in detail. It was not until they were all 

 united in the bed of the Megna, and pressed between the Tiperah 

 Hills and the upheaved tract, that the real struggle began. 



In this case, though the Megna was much the smaller river, it 

 had certain advantages necessary to be pointed out in order to appre- 

 ciate the result. 



The first of these is, that the Sylhet rivers depend wholly on the 

 monsoon rains for their supply. The clouds, striking early on the 

 Cossya range, discharge their waters with a violence hardly found 

 elsewhere ; and, as is well known, from 500 to 600 inches of rain 

 fall on the slopes of these hills during the three months of the rainy 

 season. It may also be mentioned that, owing either to the nature 



