232 Mr, Waldie’s investigations connected [No. 3,. 
fall, it is no worse as regards ready formed ammonia than the water of 
the rainy season ; and if the rough experiments on the other nitrogenous 
matter are to be trusted, it is no worse or not so bad even in this 
respect ; and comparing the results with the one observation quoted 
respecting the river Wandle as regards ammonia, the Hooghly water 
even at the worst, has the advantage. In considering this point, 
it must be borne in mind that the refuse which Calcutta can yield 
must bear but a very insignificant proportion to the great volume of 
the waters of the Hooghly compared with that which a large English 
town will yield to an English river, and more particularly London to 
the Thames. And then the purifying influences here are so much 
more active that contaminating constituents are much more speedily 
destroyed; nature with her all pervading oxygen, its power exalted 
by a tropical temperature, burning all up. ‘The water of the stream 
in constant motion presents perpetually renewed surfaces to the 
atmosphere to absorb the great purifying agent, and the importance 
of this will perhaps be more clearly manifested by comparison with 
another class of waters with which I shall conclude this paper. 
Tank Waters. 
This class is the tank waters, a few of which I have made a partial 
examination of, for the purpose of comparison. These are General’s tank, _ 
near the entrance to Park Street; Monohor Doss’ tank, near that to 
Lindsay Street, both of them on the plain round the Fort ; Dalhousie 
Square tank, supplied by the river; Cornwallis Square Tank, at the 
northern part of the town; a newly cleaned and dug out tank at 
Dhurrumtollah (supplied by Mr. Dall); and a village tank near my 
own premises, Also I have examined slightly two well waters, and 
the water of the Salt Water Lake to the east. of the town; the results 
of all will be given in one table and a few remarks appended afterwards- 
The water of the two tanks from the plain in May and June had a 
slightly putrid flavour; in August this was much less. Cornwallis 
Square tank was very low in May and putrid, had not increased very 
much in August and was still bad. The Dhurrumtollah tank was bad 
flavoured and abounded in vegetation; the Barnagore tank in May and 
June was covered with a thick coat of floating vegetation, and was very 
dirty and bad smelled, quite unfit for use even by the villagers, In 
August during the rains its appearance improved somewhat. 
