PURIFICATION OF AVATER FOR DRINKING PURPOSES 137 



unfiltered water in the several beds exhibited con- 

 siderable variations as regards the number of micro- 

 organisms, the maximum being 2,548, the minimum 

 244, and the average 792 per cubic centimetre. 



Lambeth WatenoorJcSj Thames Ditton, August 26, 1892 



Lambeth Watenoorhs, Thames Uitton, September 30, 1892 

 Filtered Water 



No. of 

 Filter Bed 



New Works : 



No. 10 



No. 9 . 



No. 8 • 



No. 7 . 



No. 6 . 



No. 5 . 

 General filter well 

 New Works 



of 



Age of Filter 



Bed in days 



3 

 24 



36 

 10 



28 



22 



No. of Colonies 

 from 1 c.c. 

 of Water 



50 

 23 

 10 



4 

 6 



