XXXIX.—NOTES ON THE ANNUAL WATER-DISCHARGE 
OF LARGE RIVERS; WITH INDICATIONS OF SOME NEW 
METHODS OF CALCULATION, sy REV. SAMUEL 
HAUGHTON, m.p., D.c.1., F.R.S. 
[Read May 19th, and June 16th, 1879.] 
Nore I. 
On the Annual Water-discharge of the Ganges, Brahmapitra, 
and Irawady. 
The Rev. Mr. Everest, in 1831-32, instituted a series of obser- 
vations and experiments on the Ganges, at Ghazipir, a little 
below Benares, and 500 miles from the mouth of the river, at the 
Hoogly. 
From these experiments, the following facts were obtained :— 
Water-discharge. 
Cubic feet per second. 
Rain (4 months), . : p - 494,208 
Winter (5 months), . - . a 2115200 
Hot weather (3 months), . ~ 36,330 
The arithmetical mean of these figures for the whole year is, 
obviously, 203,485 cubie feet per second; which gives us an 
annual water-discharge of 43°625 cubic miles, 
Now, the total length of the Himalayan ridge drained by the 
Ganges is 670 miles, and the rainfall increases from west to east: 
but the Ganges, at Ghaziptr, has received the drainage of only 
150 miles of the western end of the ridge. Sir Charles Lyell, 
following Colonel Strachey, proposed to estimate the discharge 
of the Ganges into the sea by increasing the Ghazipir discharge, 
in the proportion of 670 to 150, or to nearly 43 times the Ghaziptr 
discharge.* 
As this appears to me a very rude method of calculation, I 
have recomputed the areas of the rain-basins of the Ganges, 
above and below Ghaziptr ; and of the Brahmapitra, using for 
the purpose Mr. Stanford’s newest Orographical Map of Asia. 
I traced carefully, for this purpose, the three areas mentioned, 
* Principles of Geology (Lyell), vol. i., p. 480; London (1875). 
Scien. PRoc., R.D.S.. Vou. 11., Pr. 1v. p 
