Report on the Bacteriology of Water. 



385 



.1 



Window 

 open 



P.M. 



Red. Blue. 



C. C. 



13-0 13-0 



11-75 12-5 



11-5 12-25 f 



12-25 13-0 



13-0 13-5 J 



, 15-5 15-0 -> 



16-5 15-5 \ . 



lAta tA K I Window 



l4 ' 5 14 ' 5 f shut 



, 14.0 14-0 I 



, 11.0 iro J 



At 3.10 the exposure was stopped, and both cultures put into an 

 incubator at 22 C. in the dark, and they remained under absolutely 

 like conditions to the end of the experiment. 



The marked retardation of the blue culture, after the four hours' 

 exposure to a winter sun, never clear of haze, and at temperatures a 

 trifle higher than tho red rather than below, is well seen from the 

 following table, in spite of the careful nursing at 22 C., a very 

 favourable temperature, be it noted : 



Time. 

 11.0 A.M 

 11.30 

 12.30 

 12.40 



1.0 



1.10 



1.20 



1.50 



2.0 



3.10 



Germination had not begun at 3.10, but was commencing at 4.30 in 

 the red, whereas it was delayed till 8.30 in the blue, and would, no 

 doubt, have been still more tardy at a lower temperature. 



A review of the foregoing results where no glass was used (except 

 the thin cover slips in some) only confirms the previous results. 



1. The spores are distinctly retarded or killed by five or six hours' 

 exposure to daylight, even of low intensity, quite apart from tem- 

 perature. 



2. The growing filaments are often not measurably retarded within 

 the period observed, except under conditions such as do not exclude 

 possible temperature effects ; but the evidence goes to show that the 

 light slowly retards the growth, acting like a brake on the curve of 

 growth. 



