Report on the Bacteriology of Water. 



343 



Effect of Light from Blue Sky on Spores. 



I now made a new departure. Starting from the fear lest any 

 heating up of the bichromate, &c., screens, and the passage of the 

 solar rays through so many glass layers, <fec., might affect the results, 

 I arranged screens and cultures as follows : 



Three large circular crystallisation dishes, 12 in. wide by 4 in. 

 leep, were taken ; they were of thin clear glass, with vertical walls 

 and flat floor. These were supported, bottom down, each on four 

 corks just large enough to clear the cover-slip roofs of my cells, with 

 their hanging drops. 



