ON BACTEIUOLOGY IN ITS RELATIONS TO CHEMICAL SCIENCE. 457 



in water are carried down and removed from suspension by the sub- 

 sidence of solid particles of different kinds : — 



Memoval of Micro-organisins by Sedimentation. (Peect Frankland.) 



Agitation for 15 minutes with Chalk. 



Untreated water contained 8,000 in 1 c.c. 



After agitation 270 in I c.c. 



Eeduction = 97 per cent. 



Agitation for 15 minutes with Coke. 



Untreated water contained Innumerable 



After agitation None 



Reduction = 100 per cent. 



Agitation for 15 minutes with Animal Charcoal. 



Untreated water contained 8,000 in 1 c.c. 



After agitation 60 in 1 c.c. 



Reduction = 99 per cent. 



Agitation for 15 minutes with Vegetable Charcoal. 



Untreated water contained 3,000 in 1 c.c. 



After agitation 120 in 1 c.c. 



Eeduction = 96 per cent. 



I have recently extended these observations to the subsidence of 

 bacteria in water during storage in large reservoirs. 



Reduction in numher of Micro-organisms effected by storage of Water in 

 Ueservoirs. (Percy Frankland.) 



New River Compamj. 



Water in cutting above reservoir 077 in 1 c.c. 



Water at outlet of first reservoir 560 in 1 c.c. 



Water at outlet of second reservoir . . . . 183 in 1 c.c. 



West Middlesex Company. 



Thames water from Hampton 1,437 in 1 c.c. 



Thames water from Hampton after passing through one 



storage reservoir 318 in 1 c.c. 



Thames water from Hampton after passing through two 



storage reservoirs 177 in 1 c.c. 



The above figures show the importance of storage as a means of 

 removing bacteria from surface waters. 



Another important matter, again, in connection with the hygiene of 

 water, on which bacteriology alone can throw light, is the fate of patho- 

 genic bacteria gaining access to water. This inquiry has been pursued 

 by a number of investigators, and has led to many interesting results. 

 Amongst the most important of these I may specially mention — 



(1) That in some exceptional cases pathogenic bacteria are destroyed 

 with remarkable rapidity, in a few hours, when inti'oduced into ordinary 

 potable water. 



