Report on the Bacteriolugy of Water. 373 



XXIII. 



In the following tables I give the determinations of the numbers 

 of all bacteria found in three series of analyses of samples of Thames 

 water in August, October, and December, 1893. As will be seen, 

 they confirm the results of other observers, in so far that they show 

 that the number per c.c. is considerably greater in winter than in 

 summer. 



There is nothing special to note as regards the methods employed, 

 which were those ordinarily in use, beyond the fact that we counted 

 every colony on each plate, instead of estimating the averages from a 

 few squares. 



The greatest care was taken to have the gelatine made up exactly 

 alike in every case ; further information as to details is supplied by 

 the tables. 



