Report on the Bacteriology of Water, 



353 



L. 



posed to the light, and numbers too high to count in that covered 

 with foil and paper ; moreover, the latter plates were so badly lique- 

 fying that their marked contrast to the former could not escape 

 observation. 



It was clear that exposure to sunlight affects the liquefying powers 

 of the forms in the Thames water, and this apart either from the 

 difference in numbers on the plates or because it eliminates these 

 forms more rapidly. 



XV. 



On August 29 two flasks were prepared as before. F 11 was 

 exposed to sun with mirrors, &c., and P 12 put by its side covered 

 with foil and black paper. 



The first exposure was from 9.30 A.M. to 12.30 A.M. three hours' 

 good sunshine, though with occasional clouds. 



The water to start with was estimated to contain about 1200 germs 

 per c.c. 



After three hours' exposure F 11 gave, as the result of two plates, 



