1867.] with the supply of water to Calcutta. 143 



only to a comparatively very slight degree. At first I was inclined 

 to attribute this difference to some local or accidental cause which 

 had led me into a mistake as to the general character, hut after 

 further observation and consideration, I do not think that this is the 

 explanation, but that the water is really different in this respect, this 

 season, from what it was last. For not only has the putrid smell been 

 absent, but the mud has been easier to separate from the water ; the 

 particles are not so fine, or at least not so glutinous, and it has not 

 been so difficult to filter clear as it was last year at the corresponding 

 periods ; and the quantity of organic vegetable matter produced on 

 standing in bottles has been decidedly less than it was last year. 

 Indeed the river water of the rainy season of 1865 gave much more 

 vegetable growth than that of either of the two succeeding years. 

 Moreover the water of the river did not become muddy nearly so 

 speedily after the setting in of the rains as it did last year : this was 

 noticed particularly, as the muddy water was watched for. Neither 

 after it had become muddy, did it exercise nearly so strong a deoxida- 

 ting power on permanganate of potash as it did last year : only about 

 one-third of the power ; and this is a good indication of putridity. 

 These facts, to which may be added the greater purity of the 

 water of the hot season of this year, seem to indicate some general 

 cause producing the variation. Both 1865 and 1866 were years 

 of deficient rainfall, 62.40 and 60.32 inches ; while the year preceding 

 1865, was one of large rainfall, there having been 84.22 inches 

 in 1864. This perhaps may have some connection with the points 

 noticed. The peculiarity is worth attention in the future. 



The subject of water analysis, in connection with hygiene has 

 lately occupied much attention in London. Dr. Frankland has 

 expressed opinions respecting the small value of the oxidation test by 

 permanganate, in accordance with my own and on additional grounds 

 and also proposed a fuller examination of the nitrogenous constitu- 

 ents as the most important guide. Miles Messrs. Wanklin Chapman 

 and Miles Smith have also proposed some new methods for determining 

 the nitrogenous constituents. The details of these plans, however have 

 not yet been published, or at least have not yet come under my 

 notice. The subject is also under experiment by myself, and will have 

 further attention. 



