NUMBER OF BACTERIA IN WATER 



37 



River Thames Water Collected at Hamplo7i, 



Number of Micro-organisms obtained from 1 c.c. of Water. 



Another example from the river Lea was as follows :- 

 River Lea Water Collected at Chingford. 



Number of Micro-organisms obtained from 1 c.c. of Water. 



" During the summer months these waters are purest as regards 

 micro-organisms, this being due to the fact that during dry weather 

 these rivers are mainly composed of spring water, whilst at other 

 seasons they receive the washings of much cultivated land " (Frank- 

 land). Prausnitz has shown that water differs, as would be expected, 

 according to the locality in the stream at which examination is made. 

 His investigations wore made from the river Isar before and after it 

 receives the drainage of Munich : — 



Above Munich 



Near entrance of principal sewer 

 13 kilometres from Munich . 

 22 „ „ . 



No. of Colonies 

 per c.c. 



531 



227,369 



9,111 



4,796 



2,378 



