THE BACTERIA IX NATURAL WATERS 



VARIATIONS IN BACTERIAL CONTENT, MERRIMAC RIVER 

 Gage (1906) 



The contrast between the two classes of rivers is well 

 brought out in a study of the Lahn and the Wieseck, 

 by Kisskalt (1906) ; and the table below, compiled from 

 his data, gives an excellent idea of the total numbers of 

 bacteria and their seasonal fluctuations in a stream of 

 fair quality (the Lahn) and a highly polluted one (the 

 Wieseck), In the former case the bacterial numbers 

 are highest when rain brings surface pollution; in the lat- 

 ter, when the sewage constantly present is least diluted. 



MONTHLY VARIATIONS OF BACTERIA IN A NORMAL ANT) 

 POLLUTED STREAil 



Kisskalt, 1906 



^ Rain or high water due to previous thaw. 



