234 Mr. Waldie's investigations connected [No. 3 



The Salt Water Lake water did not require more oxygen than the 

 tank waters.* 



I have little to add in the way of concluding remarks, as my object 

 was not to report on any scheme or recommend any plan, but simply 

 to communicate to a scientific society the results of numerous experi- 

 ments and observations on a subject of practical importance. Some 

 of these investigations are defective, but I intend to endeavour to 

 remedy these defects by further investigation. And even after these 

 are remedied, the results may indicate that there are yet other points 

 o examine. There is work for the naturalist in the investigation of 

 he animal and vegetable life in such waters, possibly exercising as 

 great an influence on their salubrity as their chemical composition, 

 Yet even this can only be aided by a full and accurate knowledge of 

 their chemical constituents. There are also questions connected with 

 the preservation and use of the water, and these too are more likely 

 to be correctly answered, the more complete is our knowledge of the 

 nature of its composition. 



But I may briefly sum up the conclusions arrived at with reference 

 to the application of the Hooghly water to the supply of the wants of 

 Calcutta. As regards its inorganic constituents, the Hooghly water 

 taken near Calcutta is at least as pure as any of the waters supplied to 

 London, or indeed generally more pure for about eight or nine months 

 of the year ; during the hot season it is mixed with sea water under 

 the influence of the tides and thereby rendered brackish. This can 

 be avoided by taking the supply of water, from further up the river. 



As regards organic matter, again, my results, if correct, indicate that 

 the state of the water seems to be worst during the rainy season, and 

 that notwithstanding the influence of the tides and the sewerage of 

 Calcutta, it is doubtful if even at the hottest part of the hot season in 

 June its impurity equals that of the water during the rains ; and it is. 



* I have already stated that it was with considerable hesitation that I 

 left the indications of the permanganate Test in table III. on account of the 

 objections raised to their value : similar hesitation was felt as to inserting 

 Table IV. and it was the indications given in Table V. which determined me 

 to retain them. The same objections indeed apply to the results shewn by ifc, 

 but this does not materially affect the purpose for which it is introduced. It 

 will serve sufficiently well for purposes of general comparison, the trials for 

 oxidizable matter and ammonia having been made at the same times on both 

 river and tank waters, so that generally both kinds were of the same age or 

 nearly so. More exact determinations will be made in future. 30th Nov. 1866.. 



