Report on iJie Bacteriology of Water. 



181 



Ward, on March 8, 1892, at a point more than a mile above Staines, 

 and sufficiently distant from the Windsor district to render it very 

 improbable that any direct contamination thence need be feared ; as 

 a matter of fact, the analyses show that this water was by no means 

 rich either in bacteria or organic matter, and, for an open river, 

 was remarkably pure (see p. 182). 



As this sample was not received by me until some days after its 

 collection, the number of micro-organisms which I found in it does 

 not afford any insight into the bacterial condition of the river at the 

 time, but on this subject I have already collected a large amount of 

 information in the course of the regular monthly examinations of the 

 London water supply which I made for the Local Government Board 

 during the three years 1886, 1887, and 1888. The results of these 

 examinations, which are recorded in the preceding three tables, 

 clearly indicate (1) the seasonal variations which the number of 

 bacteria in the unfiltered waters of the Rivers Thames and Lee under- 

 goes ; (2) the great reduction in these numbers which is effected by 

 the storage and sand-filtration to which these waters are subjected at 

 the waterworks before distribution ; (3) the very small number of 

 bacteria present in the deep-well water of the Kent Company. 



Two entirely independent series of experiments have been made 

 with this sample, the difference between the two series being in the 

 number of anthrax organisms which were introduced into the 

 water. Thus in the First Series, a comparatively small number of 

 anthrax bacilli were put into the water, whilst in the Second Series 

 the number introduced was very much larger. There was this 

 further difference between the two series of experiments that the 

 Bacillus anthracis employed had a totally different origin in the 

 two cases. The use of the organism from two distinct sources in the 

 way indicated is in my opinion of great importance as eliminating 

 the possibility of any special and exceptional characters having 

 become impressed on the particular cultivation employed. 



Experiments with Thames Water (First Series'). 



We will direct our attention in the first instance to what we have 

 called the " First Series " of experiments, in which the sporiferous 

 Bacillus anthracis was introduced in comparatively small numbers 

 only into the water. 



This First Series of experiments includes four sub-series, in each 

 of which the Thames water was employed in a different condition. 

 Thus— 



(1.) Experiments made with the Thames water in its natural state. 

 (2.) Experiments made with the Thames water after removing 

 the coarser suspended particles by filtration through Swedish filter 



VOL. LIII. 



