1865.J FALCONER NILE AND GANGES. 377 



4. Analogy of the Fluviatile Deposits of the Nile with those of the 

 Ganges. — In some of the phenomena observed by all the travellers 

 above named, there is a striking analogy between the alluvial deposits 

 of the valley of the Nile and those occurring along the banks of the 

 Ganges and Jumna rivers, in the great alluvial valley of Hindostan. 

 Of these the most obvious is the great abundance of argillaceo-cal- 

 careous concretions, forming an impure kind of travertine, and in 

 the lowermost beds horizontal deposits of more or less extent, com- 

 posed of the same kind of material. Eussegger constantly alludes to 

 their frequent occurrence, both in the conglomerates and in the in- 

 durated sand- or mud-deposits, in the form of nodular concretions, 

 varying in size from a pea up to a quarter of a cubic foot, and 

 having their centres occasionally occupied by drusy cavities lined by 

 crystals of carbonate of lime. The lowermost bed, No. 5 of his sec- 

 tion, consisting of a hard dark-grey clinking limestone, appears to 

 be a modified kind of the same calcareous deposition. The nodular 

 form of these concretions is familiar to English observers in the 

 " Race," which so thickly studs the sections of the brickearth-pits 

 in many localities in the valley of the Thames. 



§ II. Fluviatile Deposits oe the Ganges. 



1. Physical Features of the Valley of the Ganges.— The vast ex- 

 panse of the plains of Hindostan consists of a fundamental deposit of 

 very ancient fluviatile sediment, which is developed in great force, but 

 varying in its detrital characters as we follow the course of the rivers 

 down to the sea. The valley is longitudinally traversed, after their 

 escape from the Himalayah Mountains, by the Ganges and Jumna, 

 which unite at Allahabad. This segment, the Doab, constituting 

 the upper division of the plains of Hindostan, is that to which the 

 remarks which follow apply. It is comparable in some respects to 

 the tract through which the " Blue " and " White " Niles flow in the 

 lower part of their course to their junction at Khartoom. The 

 Ganges at Hurdwar, where it debouches from the Sewalik Hills, is, 

 according to the results given by Sir Proby Cautley, 974 feet above 

 the level of the sea, and at Allahabad 269 feet, after running a 

 course in a straight line of 472 miles, giving an average fall of 

 nearly 18 inches per mile. Prom Allahabad to Eajmahal in Bengal, 

 near the top of the modern delta, the average fall, according to the 

 instructive table given by Mr. Fergusson, amounts to about 6 inches 

 along a stretch of 385 miles. The Jumna river, where it escapes 

 from the Sewalik Hills at Eajghat, is a little more elevated ; but it 

 runs a nearly parallel course at no great distance from the Ganges, 

 and in the inclination of its bed and other physical phenomena it 

 resembles that river so closely that in the present sketch it is not 

 necessary to dwell on the points of difference. 



Although the average inchnation of the Ganges between Hurdwar 

 and Allahabad is about 18 inches per mile, it increases considerably 

 as we ascend the river. Thus the faU, which in the distance of 122 

 miles between Cawnpore and Allahabad diminishes to 13 inches, at- 

 tains in the mean of the 350 miles above it 19*3 inches, and so on 



