Report on the Bacteriology of Water. 

 (A.) Bulb not Blackened. 



323 



(B.) Bulb Blackened. 





These examples will suffice to show how far the screens differ as 

 regards transmission of heat rays. 



The following series is interesting as showing that the thermometer 

 hanging in the glass bell-jar, with its bulb close to the culture- 

 chamber, may undergo considerable variations without any corre- 

 sponding reaction in the growth curvatures. 



The experiment was designed to see if the light of a paraffin 

 lamp would be sufficiently active to affect the growth ; but the 

 results showed that for short periods, at any rate this is not the 

 case. As is well known, however, the flame of a paraffin lamp is 

 very hot, and the possibility arises that the rise of temperature may 

 mask the effect, if the paraffin light has any. 



