Report on the Bacteriology of Water. 331 



Third Culture, at Lower Temperature at North Window. 



Total growth = 55 /* in three hours eight minutes, which at constant 

 rate =0'29 /t per minute. 



The scrutiny of these tables can leave little doubt that the general 

 shape of the curves is due to the temperature, and the curve at 

 the lower temperature is hardly useful for any other purposes. 



As regards the other two curves, however, the sharper ascent of the 

 curve of the dark culture from 1 o'clock to 2.30 requires explanation, 

 and, unfortunately, the data do not quite suffice for it. Of course, 

 the suspicion arises that it may be due to the inhibiting action of 

 light so retarding the growth in the one case, that the darkened fila- 

 ment although a younger, and therefore more feebly growing speci- 

 men to begin with is gradually making way and more than catching 

 it up. 



The following comparative observations were made with the dummy 

 cells, between CuS0 4 and bichromate screens, top and bottom, on a 

 bright day in March. 



Here, again, it is evident that the observer must be very carefully 

 on his guard when using these screens, of glass bottles containing 

 liquids which filter out different rays, of different heating power ; 

 and I would also call attention to the matter of the heating up of 

 these screens in the sun and their power of slowly radiating their 

 heat later on. 



Temperature of cell in 



Time. 



lO'O A.M. ... 

 11-30 ... 

 12-15 P.M.... 

 12-30 ... 



