Report on tie Bacteriology of Water. 



355 



The rodlet therefore grew 248 4 ft in three hours fifty-three minutes, 

 which gives over 1 /t per minute at constant rate i.e., more than 

 10'8 per cent, of the original length. 



The doubling periods = 



1. 9-2 18-5 ft in 25 minutes at 26 27'5 C. 



2. 18-537-8 23 27'5 constant 



3. 37 74 |f 47 27-5 17-5 C. 



4. 74 148 75 17'5 18 C. 



Culture in Dark. 



Doubling periods = 



1. 6-6 13-2 f i in 40 minutes at 2324 C. 



2. 13-2 26-4 95 2421 C. 



3. 26-4 52-8 86 2120 C. 



4. 52-8105-6 82 20 C. 



I am unable to explain the slow rate of growth except on tie 

 hypothesis that the heat was rapidly radiated from the thin glasses* 

 on lifting the bell, and so kept the culture back. 



Another possible perhaps more probable explanation is that the 

 screens absorb (and subsequently radiate) heat from the solar rays; 

 whereas the bell-jar did not do this to the same extent. The tempe- 

 ratures in the dark being, therefore, lower throughout all the early 

 stages of the observation (only the air-temperature could be obtained 

 owing to difficulties of manipulation) explains the effect. 



Comparisons of the tables and curves of the two light cultures 



