232 Mr. Wattle'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. 



