470 Professor Faraday, [Feb. 12, 



Many of these forms of animal and vegetable life are not in- 

 jurious in themselves ; but they are most numerous where there is 

 the greatest amount of impurity, and are a measure of the greater 

 or less objectionable nature of a water for drinking purposes. They 

 were not present in water freshly drawn from deep wells. 



From these circumstances it was concluded, that the water from 

 deep wells was most desirable and unobjectionable as drinking 

 water ; that the water from surface wells ought under no circutn- 

 stances to he drunk at all; and that if Thames water was used, it 

 ought to be filtered, or what is better, boiled and filtered. Boiling 

 expelled the carbonic acid from water, and rendered it vapid ; but 

 its briskness might be restored by passing it through the gasogene. 

 In the filtration of water various agents may be used, as sand, 

 sponge, charcoal, rock, &c. The most effectual is animal charcoal, 

 which may be introduced into any of the ordinary forms of filter. 

 Dr. Medlock had shown that the addition of iron to water con- 

 taining organic impurities, precipitated them without rendering the 

 water metallic. Water, which had been filtered in contact with 

 iron twelve months since, was exhibited and compared with water 

 which had not been thus filtered ; the latter showed a large quan- 

 tity of impure .vegetable growth, whilst the former was quite pure. 

 Water, which had been obtained from the wells at Watford three 

 years ago, was also exhibited, and showed no signs of vegetation ; 

 also water which had undergone " Clark's process," and was equally 

 pure. 



[E. L.] 



WEEKLY EVENING MEETING, . 

 Friday, February 12. 



H.R.H. The Pbince Consort, K.G. D.C.L. F.R.S. Vice-Patron, 

 in the Chair. 



Professor Faraday, D.C.L. F.R.S. 

 Remarks on Static Induction. 



The object of the speaker was to give to the Members of the Royal 

 Institution a simple reference to the production and nature of the 

 static phenomena of electricity ; especially in respect of induction, 

 into which indeed they all resolve themselves. When flannel, 

 shell-lac, metal, and sulphur, are any two of them rubbed together 

 they become electrified in the well-known manner ; and in such order 



