388 



Dr. P. F. Frankland. 



[June 18. 



was first tested for the number of organisms contained in the water 

 nsed in the experiment. After eighteen hours the two bottles to 

 which lime-water had been added were tested withont disturbing 

 the precipitate, and also the third bottle containing the untreated 

 water which had been left at rest in the same place as the other two. 

 The following results were obtained : — 



Untreated water 85 centres per c.c. 



„ „ after 18 hours' rest 1,922 „ „ 



Water after Clark's process and 18 hours' 

 subsidence 42 „ 



In order to appreciate the real effect of the treatment by Clark's 

 process, it is necessary that the treated waters should be compared, 

 not with the original water, but with the latter after eighteen hours' 

 rest, for this shows what the condition of the water would have been 

 at the time of testing if no lime-water had been added. It is evident 

 that after the subsidence of the carbonate of lime precipitate has taken 

 place, there is every probability of the organisms becoming again 

 distributed throughout the upper layers of the water, and with a 

 view of determining whether this actually takes place or not, the 

 same waters which had remained well stoppered and at rest were 

 again tested after the lapse of ten days. It was then found that the 

 untreated as well as the softened waters contained immense numbers 

 of organisms in their upper layers. 



As the effect of Clark's process in removing organisms from water 

 appeared to be of great practical importance, the above experiments 

 were repeated, the conditions being essentially the same as before. 

 The following results were obtained : — 



Untreated water 37 centres per c.c. 



„ „ after 21 hours' rest 42 „ ,, 



„ „ after 48 hours' rest 298 „ „ 

 Water after Clark's process and 



21 hours' subsidence .......... 22 ,, „ 



Water after Clark's process and 



48 hours' subsidence 166 „ „ 



Owing to the number of organisms in the original water having 

 been very much smaller, the results are not so pronounced as in the 

 former case, the main facts are, however, fully substantiated. 



It appeared also to be of interest to ascertain what results are 

 obtainable on the large scale. For this purpose the process of soften- 

 ing as practised at the Colne Valley Waterworks at Bushey, near 

 Watford, was investigated, as well as the new modification of Clark's 

 process devised by Messrs. Gaillet and Huet, which is now in opera- 

 tion at Mr. Duncan's, Clyde Wharf, Victoria Dock. I am indebted 



