22 Comparison of the Indus and Ganges Rivers. [Jan. 



more consistent banks than the other river, and, as I have shewn in my 

 memoir, seldom exceeds half amile in width ; the Ganges, on the other 

 hand, is described as an inland sea in some parts of its course, so that 

 at times the one bank is scarcely visible from the other, a circumstance 

 which must greatly increase the evaporation. The arid and sandy 

 nature of the countries that border the Indus soon swallow up the over- 

 flowing waters, and make the river more speedily retire to its bed. 

 Moreover, the Ganges and its subsidiary rivers derive their supply from 

 the southern face of the great Himalaya, while the Indus receives the 

 torrents of either side of that massy chain, and is further swollen by 

 the showers of Cabiil, and the rains and snow of Chinese Tartary. Its 

 waters are augmented long before the rainy season has arrived ; and 

 when we look at the distant source of the river, to what cause are we 

 to attribute this early inundation, but to melting snow and ice. 



" The slope on which the Indus descends to the ocean would appear 

 to be gentle, like that of most great rivers. The average rate of its 

 current does not exceed 1\ miles an hour, while the whole of the Pun- 

 jab rivers, which we navigated on the voyage to Lahore, were found 

 to be one full mile in excess to the Indus ; we readily account for this 

 increased velocity by their proximity to the mountains, and it will serve 

 as a guide in estimating the fall of the great river. The city of Lahore 

 stands at a distance of about 1,000 British miles from the sea, by the 

 course of the river ; and I am indebted to the kindness of Dr. J. G. 

 Gerard, of the Bengal Establishment, for a series of Barometrical obser- 

 vations made at Amritser, a city about 30 miles eastward of Lahore. 



The mean of 18 of these observations gives us the 

 height of the Barometer at 28.8613 



The corresponding observations at Calcutta give.. . . 29.7115 



Making a difference of.. . . . .8502 



li I am informed, that the height of instrument registered in Calcutta 

 may be 25 feet above the level of the sea, and as the city of Amritser 

 is nearly on the same level as Lahore, (since both stand on the plains 

 of the Punjab,) it must have an elevation of about 900 feet from the sea. 

 It remains to be considered in what and how great a proportion this 

 slope is to be distributed among the rivers from Lahore downwards. 

 On a comparison with the Ganges, we cannot give a greater fall down- 

 wards from Mittun, where the Indus receives the Punjab rivers, than 

 6 or perhaps 5 inches per mile ; nor can we allow more than l-4th of 

 the 900 feet as the height of that place about the level of the sea, for the 

 river has not increased here in velocity of current, though we have neared 



