44 



never could be an excuse for the continuation of pollution 

 by our towns, as the stench that is emitted during this 

 self-cleansing process is very dangerous and offensive, and 

 before self-purification is effected the distance travelled 

 over is considerable. 



The following interesting experiment has been lately 

 made by Mr. J. W. Slater : He took three kinds of water ; 

 (ist) raw undiluted sewage obtained from Aylesbury ; (2nd) 

 similar sewage partially purified ; and (3rd) sewage fully 

 purified as it passes from the works of the Native Guano 

 Company into one of the branches of the Thames. The 

 sewage in question is strongly animalised, containing, in 

 addition to the usual excrementitious matters and liquid 

 household refuse, a somewhat unusual proportion of blood 

 derived from the cattle slaughtered in Aylesbury for the 

 London dead-meat market. Of each of these three kinds 

 of water, the one half was filtered, and the other left in its 

 original state. He had then six kinds of water. He then 

 placed each portion in a white glass pint-bottle loosely 

 stoppered, and arranged on a shelf exposed to the morning 

 sun. In some of the bottles the stratum of water was i-J 

 inches in depth ; in others 3, 4, and up to 6 inches. He 

 now regularly examined the bottles, to take note of the 

 changes that would take place. In the bottle containing 

 the best purified water a green confervoid vegetation ap- 

 peared in a couple of days ; it increased, and bubbles of 

 oxygen were formed and rose to the surface ; there was no 

 offensive odour. Similar phenomena were observed later 

 in the other bottles ; but eight weeks passed over before 

 green vegetation appeared in the bottle containing 6 inches 

 in depth of raw unfiltered sewage. In the meantime, the 

 odour given off from this bottle had been very offensive, 

 and a small quantity of white sewage fungus appeared, 



