Water and Ice 191 



typhoid fever, is concerned. For it has been 

 shown over and over again, by the most care- 

 ful and elaborate experiments and examina- 

 tions, that the small so-called faucet filters, 

 and pretty much all the reservoir domestic 

 filters, do not separate the bacteria from 

 contaminated water in a reliable way. The 

 water is often strained by them and so 

 freed from its coarser floating particles, and 

 then may appear quite clear and limpid, 

 and some of the bacteria may be at first re- 

 moved; but after a little while not only do 

 these small filters let the invisible bacteria 

 through their pores in large numbers, but 

 they may actually afford breeding- and lurk- 

 ing-places for the living germs, the disease- 

 producing forms among the rest. 



Filtration on a large scale in properly 

 arranged systems appears to be the only 

 reliable way of freeing contaminated water 

 mechanically from its bacterial ingredients. 



Boiling of water for half an hour will, 

 however, kill the bacteria, and to this, in the 

 last resort, the householder must have recourse 

 to when the water supply is justly suspected 



