Report on the Bacteriology of Water. 389 



Bichromate. Water. 



Time. C. C. 



9.15 A.M. 17-5 17-5 



9.55 18-0 18-0 



10.40 18-5 18-5 



11.30* 19-0 19-0 



11.55 19-0 19-0 



12.20 P.M. 19-0 19-0 



At 12.20 the cultures were put into the dark incubator at 22 C., and 

 examined occasionally during the afternoon, with the following 

 results. 



At 3 P.M. there were several germinating rodlets in the bichromate 

 culture, measuring from 4'5 p. to 15'75 fi ; but none could be found in 

 the water-culture more than 2 fi long swelling spores, in fact. 



At 4.30 P.M., however, no differences of importance between the 

 two cultures could be detected. I measured 15 rodlets all that 

 could be found in the bichromate culture, and these ranged from 

 5 ft to 64^; while fourteen measurements in the water culture gave 

 from 4'5 ft to 54 /t, a difference that could not be insisted upon. 



It must be concluded from this that the above exposure (3 hours) 

 has no marked effect on the spores. It is, perhaps, worth mention 

 that a reflection of the western sun, on a hazy day (July 13) 

 thrown from a plane mirror on to the disc of light given by the lamp 

 at about 10 ft. was much brighter than the disc. 



After the foregoing, it need hardly be said that 1^ hours' exposure 

 experiment from 1.35 to 3.5 P.M. on July 14 gave no results. 



On July 16, with the same arc, but at 2 ft. distance, I exposed two 

 cultures, arranged exactly as before, for six hours viz., from 9.35 A.M. 

 to 3.45 P.M. 



The temperature slowly rose from 16'75 (bichromate) and 17'25 

 (water) at 9.35 to 18 in both at 9.50; to 20 C. at 12.50, and finally 

 to 21 at 3 P.M., but never passed beyond that. 



At 3.50 the cultures were placed in the dark incubator at 22 C. 

 Neither showed any signs of growth up to 10.30 P.M., but at 12 noon, 

 on the 17th July, the culture over water showed one weak tuft of 

 filaments, the longest being 140 to 180 /JL long ; those in the bichro- 

 mate culture were 675 to 800 n long. 



This indicates a feeble light action, no doubt ; but it is remarkable 

 that the bichromate culture had not made more progress in the time ! 



On July 26, with exactly similar arrangements, two broth drop- 

 cultures were exposed, from 9.30 A.M. to 3.30 P.M., a full six hours. 

 The temperature rose from 19 at 9.30, to 21'5 at noon, and to 22 at 

 1 P.M., and so to the end. 



* Five minutes were occupied in replacing the carbons. 



