WATER FILTERS 91 



the purity of their water supply and thus to protect 

 themselves from the epidemics of typhoid which pre- 

 vail where the drinking water is impure. 1 



Small filters. The attempt to render water pure by 

 rapid nitration through small niters attached to faucets, 

 is useless. Slow filtration through unglazed porcelain, 

 as in the Pasteur filter, is effective, but is ordinarily 

 too slow for general use. The most satisfactory method 

 of protecting ourselves against suspicious water is by 

 boiling the water and then shaking it up with air. In 

 this way, the boiled water is made palatable through 

 the restoration of the gases driven out by the heat. 



Water as a beverage. Water satisfies fully the needs 

 of the body for fluids. When drunk cold, however, it 

 has for certain persons a depressing effect. Hot water, 

 especially when sipped, does not depress but rather stim- 

 ulates the processes of digestion. Since hot water has not 

 an agreeable flavor, certain substances, as salt, sugar, 

 cocoa, chocolate, tea and coffee, are ordinarily intro- 

 duced. Unfortunately, some of these substances used 

 for flavoring are harmful. 



Cambric tea. Perhaps the best warm drink is that 

 simple mixture of milk, sugar and water, called cambric 

 tea. This warms and stimulates and has no harmful 



1 The following table shows the death rates from typhoid fever 

 in the city of Lawrence per 10,000 of population, for the 4 years 

 immediately preceding and the 4 years immediately following the 

 introduction in 1893 of sand filtration for the water of the 

 Merrimac River: 



Preceding change Following change 



1889 12.7 4.7 1894 



1890 13.4 3.1 1895 



1891 11.9 1.9 1896 



1892 10.5 1.6 1897 



During 1893, 1894 and 1895, a considerable number of persons 

 were still using unfiltered water and were responsible for about 

 half the deaths in those years. 



