1866.] with the supply of water to Calcutta. 205 
12 grains per Imp. gallon during the months of April, May and 
June; and this increase in quantity and deterioration in quality is 
considered to be due to the organic impurity from the sewers and banks 
at Calcutta. The analyses, I may observe, were chiefly made on samples 
taken at high water, obviously to get the water at its worst. Analyses 
are also given of the waters of two tanks inthe Maidaun or plain round 
Fort William, namely Monohur Doss’s Tank and General’s Tank, 
which are considered as unquestionably superior to the river water. 
I may observe that, when I commenced this investigation, it was not 
in connection with the water supply of Calcutta at all, or even in con- 
nection with the economical use of water or its wholesomeness as a 
beverage. These enquiries had been placed in the hands of others ; but 
it occurred to me, that residing, as I did, on the banks of the Hooghly, 
and possessing certain facilities for the purpose, it might be a contribu- 
tion to science of some small value to make a minute examination of 
the constituents of both the water and the mud of a great river 
draining so large an extent of country as the Ganges. The investiga- 
tion is as yet far from completion, but during its course, it occurred 
to me that many of the results obtained might have some value in 
relation to the subject just adverted to—the economical use of water ; 
and that the local interest attached to it might render it in some 
degree appropriate to publish these results, more particularly at a 
time when all the knowledge attainable connected with the subject 
is desirable. 
This communication then is not intended to present a full statement 
of the composition of the Hooghly water, but only to treat of such 
points as are of more particular interest in connection with its applica- 
tion to supply the wants of the inhabitants of Calcutta. And indeed 
this is all that is necessary for the purpose in view. As regards the 
general composition of the river water at different seasons of the year, 
my own results only go to confirm those already given in Dr. Mac- 
namara’s Report, but in some particulars, not of minor importance, the 
results I have obtained and the conclusions drawn from them are 
somewhat different ; and in other particulars it may be found that I 
have added to the stock of information on the subject. 
It is scarcely necessary to allude to the course of the seasons in 
Bengal and the way in which they affect the river. But for 
