OF THE NILE AND GANGES. 639 



so closely tliat in the present sketch it is not necessary to 

 dwell on the points of difference. 



Although the average inclination of the Ganges between 

 Hurdwar and Allahabad is about 18 inches per mile, it in- 

 creases considerably as we ascend the river. Thus the fall, 

 which in the distance of 122 miles between Cawnpore and 

 Allahabad diminishes to 13 inches, attains in the mean of 

 the 350 miles above it 18*3 inches, and so on upwards as we 

 ascend. The sedimentary deposits and transported materials 

 vary, as a general rule, in the same ratio. The northern 

 slope of the Sewalik hills is overlain with a thick mass of 

 boulder- gravel, inclined at a considerable angle, and con- 

 formable to the sandstone strata of which this Miocene range 

 is composed. The boulders vary from a few inches to upwards 

 of a foot in diameter ; they have undergone the utmost amount 

 of attrition, being constantly smooth and rounded into more 

 or less of a globular form. Their origin is distinctly shown, 

 as they are invariably composed of some of the rocks which 

 form the intramontane portion of the nearest river-channel, 

 transported by violent torrential action during the protracted 

 season of flooding. Modern boulder-dejections of precisely 

 the same character, and derived from the same rocks, are 

 seen in progress of formation where the rivers debouch into 

 the plains, constituting rude deltas, having a flattened conoid 

 surface, the base of which is ultimately confounded with the 

 plains. This gravel and boulder alluvium disappears from 

 the surface and along the beds of the rivers within a short 

 distance from the hills, and is replaced by a sand or clay 

 alluvium, which becomes the prevailing deposit down to the 

 confluence of the two rivers at Allahabad. It marks the 

 boundary of the habitat of some of the characteristic ver- 

 tebrate forms of the Granges, such as the Gharial Crocodile 

 (Gavialis gangeticus) and the freshwater Porpoise (Platanista 

 Gang etica), which ascend to within thirty or forty miles of 

 Hurdwar, where the gravel-beds and rapids of the stream 

 terminate ; while the Crocodilus bombifrons is met with in the 

 dhoons or longitudinal valleys which lie between the Hinia- 

 layahs and the Sewalik hills. 



The rivers which traverse the alluvial plain of Hindostan 

 have produced the usual effects of powerful fluviatile action 

 operating during a long lapse of ages, aided by movements 

 of upheaval or depression, distinct evidence of which has been 

 brought to light by deep borings in the delta. The two 

 principal streams have gradually scoured their channels down 

 through the ancient alluvium to a depth of from 100 to 150 

 feet below the level of tbe adjacent plains, thus exposing a 

 very instructive section of great extent. At the lower part 



