XXXIV. J. M. SMAIL. 



alone — the Jewell Filter Company — has constructed plants 

 in various towns in North America, the aggregate capacity 

 of which is equal to 400 million Imperial gallons daily, about 

 equal to the quantity filtered under the slow filtration 

 method in England and Wales. The necessity for a different 

 method of treatment is no doubt owing to the turbidity 

 of the rivers and the enormous consumption per capita as 

 compared with European cities; the consumption in some 

 cities is enormous. 



The American engineer takes the water as it comes from 

 the river, treats it with a coagulant — sulphate of alumina — 

 which brings about the aggregation and deposit of the 

 greater pari «»j' the suspended matter. By this means from 

 40 to 75 of both suspended matter and bacteria is removed 

 before it reaches the filter bed, and this is performed in as 

 many hours as it would take days in ordinary subsiding 

 reservoirs. 



The relative advantages claimed in comparison with slow 

 sand filters are : — 



1. Capacity to treat very turbid waters. 



2. Capacity to remove a large percentage of colour. 



3. Occupy a relatively insignificant area of ground. 



4. Protection from weather. 



5. Freedom from risks of objectionable growths, and 



from tastes and odours they impart. 

 0. Rapidly and easily cleansed, without risk of con- 

 tamination by workmen. 



7. Sand bed can be easily and economically sterilized. 



8. Absolute control of each separate filter, together 



with complete knowledge of its condition. 



9. Allow water to be sent straight to the consumer 



with the least possible delay and expense. 



Having stated the advantages claimed for this system, 

 it will be necessary to see how these claims are supported 



