568 Adeney — Dissolved Gases and Fermentative Changes. 



It should be noted that the tap-water used for diluting the sewage-water 

 suffered but little, if any, change during the period of keeping. 



Although the results afforded by this series of results were definite enough to 

 warrant the conclusions I have formulated, they could not be considered as 

 constituting a sufficient basis for extending these conclusions to polluted and 

 natural waters generally. 



Other waters, whether polluted with sewage-matters or vegetable matters such 

 as peat, might contain fermentable substances of different composition, and 

 organisms of different chemical functions ; and such waters, when similarly 

 examined, might give rise to results which might lead to different conclusions. 

 It was therefore necessary to extend my observations to polluted and natural 

 waters differing widely in character from one another. 



I first, however, made some further experiments with other samples of sewage- 

 water taken from the same locality as that from which the sample employed in 

 my first series of experiments was taken. These confirmed the results I have 

 already given, and need not be recorded here. 



As examples of results obtained with sewage-water from quite a different 

 locality, I will give those of two series of experiments with two samples, for 

 which I was indebted to the kindness of Mr. J. C. Melliss, C.E., of London. 

 Both samples were taken on June 21st, 1893, from the Riclimond Main Drainage 

 Works, near London, one being of raw sewage before treatment, and the other of 

 sewage- water after clarification with lime and sulphate of alumina, and a very 

 careful filtration through one of the gravel filter-beds with which the works are 

 furnished. Each sample was an average of portions collected hourly from 

 6 A.M. to 6 P.M. 



The raw sewage was filtered and aerated, and the following dilutions were 

 made as before : — 1 volume of raw sewage to 9, 19, 39, and 79 volumes of tap- 

 water. The particulars of the experiments are given in the subjoined Table ; — 



