CLEAN- DRINKING-WATER. 245 



means of conveying malarial poisons to places at a distance," "by dis- 

 tributing organic matter held in suspension. Dr. Edwards, of Mont- 

 real, found two grains of organic matter to the gallon of melted 

 shore-ice, and one grain to the gallon of river-ice. One writer, Pavy, 

 says, " River water and the water of shallow wells should always be 

 reo-arded with suspicion," and he adds, " There is evidence to show 

 that the most serious consequences have arisen from the consumption 

 of impure water." Buck, in " Hygiene and Public Health," says, 

 " The weight of evidence and authority favors the idea that the drink- 

 ing-water may become the cause of disease, and in drinking a polluted 

 water one always runs more or less risk." The River Pollution Com- 

 mission of London, after analyzing water from different sources, re- 

 ported dangerous " river- water to which sewage gains access." 



The conclusion from the above quotations is, not that one should 

 abstain from drinking water on account of the difficulty in obtaining 

 it pure, but that proper precautions should be observed to obtain it 

 pure. Water is Nature's means of slaking thirst, and with its refresh- 

 ing properties combines valuable therapeutic qualities. 



An excellent article, published in the " Boston Journal of Chem- 

 istry," in treating of the curative value of water says : " We notice the 

 salutary influence of water-drinking upon many of those who resort to 

 the so-called mineral springs which abound in the country. It is not 

 necessary that these springs should hold abnormal quantities of salts 

 of any kind to effect cures ; it is only necessary that the water should 

 be pure. Ordinary springs, such as are found in every farmer's past- 

 ure, are curative springs if the waters are used freely by those who 

 suffer from certain gastric or renal difficulties." This writer asserts 

 that the best known of our Eastern mineral waters shows, on analysis, 

 that its curative value consists solely in its purity. 



It may be truthfully asserted that it is impossible to procure per- 

 fectly pure water. " Even distilled water and fresh rain-water contain 

 some ammonia, carbonic acid, and other matters which detract from their 

 purity ; while the best water from rivers, wells, ponds, and tanks, con- 

 tains a large number of chemical compounds, chiefly salts." The skill- 

 ful use of the microscope would condemn the water from many sources 

 for drinking purposes which now is considered pure. But while we 

 can not obtain strictly pure water, even by distillation, we can obtain 

 it so pure that it will meet our demands, and that without danger to 

 the consumer's health. The means by which this may be accomplished 

 is filtration. 



A filter is an apparatus for separating from fluids the foreign sub- 

 stances mechanically intermixed with them and held in suspension. 

 While this is all that most filters aim to accomplish, yet experiments 

 show that a filtering material may be used which very markedly di- 

 minishes the foreign bodies usually held in solution in water, and also 

 removes those held in suspension. 



