218 Proceedings of the Asiatic Society. [Oct. 



length of time the water had been kept after collection before the 

 analyses were made, as high chemical authority could be adduced for 

 the necessity of commencing the analysis without delay. Now he 

 could not but admit that there had been more or less delay in com- 

 mencing the analysis of the greater part of his samples, as he was not 

 aware that such conclusions had been arrived it ; and he had himself, 

 from consideration of the great exposure that surface waters supply- 

 ing a river had already undergone, rather formed the opinion that the 

 decomposition of the organic matter would probably have pretty well 

 reached the maximum, so as not to leave much room for further decom- 

 position. His own observations had confirmed him in this so far as ex- 

 tended keeping was concerned ; but as there possibly might be a certain 

 amount of rather rapid decomposition during the first week or two 

 which he had overlooked, it appeared desirable to endeavour to ascertain 

 the truth of this or otherwise, if possible. With that view he had, during 

 the last month, made a considerable number of experiments and analyses. 



The plan of testing by the oxidising action of permanganate of pot- 

 ash offered the readiest means for doing so, and this certainly indicated 

 a distinct diminution of the amount of oxidizable matter, and a ra- 

 pid one too, occurring even within the first twenty-four hours. But 

 though the diminution was considerable, sometimes one-third or one 

 half of the whole amount, yet the absolute quantity was small ; and 

 besides, this mode of testing gave no reliable information respecting the 

 quantity of all the organic matter, which was the point at issue, and 

 which could only be determined by ascertaining its weight. 



As the question principally had reference to the water of the hot 

 season, and of course no recent water of this kind could be procured, 

 mixtures were made to imitate it, from samples of hot season water 

 which had been kept, with additions of portions of sewage water. 

 Such were prepared and the organic matter in them determined imme- 

 diately, and afterwards at an interval of 12 or 14 days. A diminution 

 was found to have taken place, but to a comparatively small extent, even 

 though it was found that a considerable degree of putrefaction took 

 place in them. But these mixtures, though containing from T ^- to -£- of 

 sewage, contained only from 11 to 4 J grains organic matter per gallon ; 

 and yet, from their smell and other properties, it was quite impossible 

 that the river water could be at all like the two worst of them. Be- 



