1867.] 



with the supply of water to Calctitta. 



123 



properties. I have paid some attention to the subject, but am not at 

 present prepared to discuss it. It will be matter for further examina- 

 tion. 



At present, however, it has been brought forward to justify so far the 

 comparatively unfavourable opinion I have expressed, of the value of 

 the permanganate process as a guide to enable us to judge of the 

 quality of a water as respects its salubrity. I could bring forward 

 other reasons and adduce experiments, but as I do not intend to apply 

 the method to the matters under investigation in this paper, only one 

 other instance as an additional reason for rejecting it will be adduced. 



I shall extract two or three numbers from the preceding table and 

 place beside them a few others of waters from other sources, namely, 

 from the Circular canal which connects the river at the northern 

 extremity of the town with the Salt Water Lake. This Circular canal 

 receives much the greater part of the sewerage of Calcutta. Reference 

 will again be made to it and to the Salt Water Lake. Dalhousie Square 

 Tank is filled from the river and the water is considered good ; 

 General's Tank is filled by the rains and is generally said to be the 

 best drinking water in Calcutta. 



Table IV. 







Oxygen reqd. 







for 100,000 







grains. 



Dalhousie Square Tank Water of 9th 







October, 1866, 



16 hours old, 



.0860 



General's Tank Water of 6th February, 



3 hours old, 



.2830 



1867, 



26 hours old, 



.1155 



Circular Canal Water of 23rd Novem- 







ber, 1866, 



20 hours old, 



.0832 



Ditto of 20th February, 1867, 



16 hours old, 



.0680 



Salt Water Lake water, flowing from 







Canal, 14th February, 1867, 



20 hours old, 



.1780 



Salt Water Lake of 18th February, 







from Canal at Dhappa, 



19 hours old, 



.1475 



From the Marsh, 



19 hours old, 



.1690 



In his report on the London waters to the Chemical Society on 

 March 13th, 1866,* Dr. Frankland is stated to have expressed surprise 

 that the soft water supply from Loch Katr ne required more of the 

 permanganate than any of the waters of th ; Metropolitan districts, 

 but here is something more surprising still. The water of the Canal 

 * Chemical News of 23rd March, 1866. 



