188 MICROORGANISMS IN WATER 



organisms than that on the windward side, which was 

 sheltered by the bank, and on this account samples 

 were collected on both sides, with the result recorded 

 above, that the water on the sheltered or windward 

 side did actually yield fewer colonies than that on 

 the more disturbed or lee side of the reservoir. It 

 should be pointed out, however, that the real reduction 

 in the number of bacteria effected by this storage was 

 undoubtedly very much greater than that which is 

 indicated by the above figures, for the reservoir must 

 have been filled with Thames water, containing, as our 

 previous experience leads us to know, a much larger 

 number of micro-organisms than was present in the river 

 at the time l these experiments were made. 



The second series of experiments on Thames water 

 was made on October 3, 1892, at the works of the West 

 Middlesex Company at Barnes. Here the Thames water, 

 pumped at Hampton, is made to pass through one, and 

 in some cases two, storage reservoirs before being con- 

 ducted on to the filter beds. Samples were collected of 

 the Thames water coming directly from Hampton ; 

 secondly, of the water after having passed through one 

 storage reservoir only ; and thirdly, of the water after 

 having passed through two storage reservoirs. 



The following results w r ere obtained : 



Number of Colonies 

 obtained from 

 1 c.c. of water 



1. Thames water from Hampton .... 1,437 



2. Ditto after passing through one storage 



reservoir ....... 318 



3. Ditto after passing through two storage 



reservoirs 177 



Another series of experiments on the effect of storage 

 was carried out at the Stoke JSTewington works of the 

 New Eiver Company, which were visited on August 27, 



1 See Tables, pp. 121-123, showing the variations in the number of 

 bacteria in Thames water at different seasons of the vear. 



