164 Transactions of the 



Society, I had occasion to assist at the examination of a sample of 

 water obtained from a well in the neighbom'hood of Drury Lane, 

 and suspected to contain im2:)urities. To a portion of the w^ter Mr. 

 Lewin added a small quantity of pure cane-sugar, and in less than 

 twenty hours the mixture became turbid, and the hquid when 

 submitted to a microscopical examination was found to be literally 

 alive with minute bacterian-Hke bodies in an extremely active 

 condition ; and it was obvious that these little organisms by their 

 action on the cane-sugar were the immediate cause of the turbidity. 

 The water was bright, and there was certainly nothing in its ap- 

 pearance to cause any suspicion that it was contaminated with 

 sewage. Subsequently it was ascertained that the drain-pipes of 

 an urinal not far fr'om the well were stopped up, and that the earth 

 around the well was saturated with urine. On being informed of 

 this fact, and recollecting that the characteristic fungus mycelium 

 had not been observed when the water was submitted to the sugar 

 test, I made various experiments with mixtures of urine, in different 

 stages of decomposition, and New Eiver water, and in every instance 

 failed to discover any distinctive fungus mycelium, the field being 

 almost exclusively occupied by bacterian bodies. 



About six weeks after this I accidentally made the observation 

 that water which had been passed thi'ough animal charcoal became 

 turbid when submitted to the sugar test, and that a large develop- 

 ment of bacterian bodies was produced. I had purchased a new 

 charcoal filter in the month of September last, and I was naturally led 

 to try the water by the sugar test before and after filtration, when to 

 my surprise I found that the filtered water became turbid, while 

 that which had not been filtered remained bright. This result at 

 first puzzled me, but as I had observed last summer, dming the 

 com^se of my experiments on fungi, that phosjDhate of lime exercised 

 powerful deteriorating properties by promoting the development of 

 organisms, I was led to attribute the presence of the bacteria in 

 the water after filtration to the action in some way of the phosphate 

 of lime in the animal charcoal. The mystery of this action of the 

 animal charcoal has since been explained, as it is known to be a fact 

 that a portion of the phosphate of hme in the charcoal is dissolved 

 out by the water when passing tkrough it. 



I have made some special experiments with phosphates in pure 

 distilled water, under various conditions, and the results showed 

 that in every case when phosphate of lime was present, the hquid, 

 on the addition of cane-sugar thereto, became turbid and literally 

 alive with bacteria, in times varying from twelve to thirty hours. 

 The phosphates of the alkalies gave negative results, but when nitrate 

 of ammonia was present, a slight turbidity occurred after the lapse 

 of several days, and the liquid was found to contain a few bacteria. 

 The results of these experiments confirmed my previous observa- 



