HEALTH AND WELL-BEING 57 



supply on the farm and in the city. Disease germs in the water may 

 cause widespread sickness and death. Water from surface wells and 

 streams is always subject to suspicion when not safeguarded with the 

 greatest care. 



The source of the water supply for different cities, and the manner 

 of its purification, varies according to local conditions. In some cases 

 it is pumped from deep wells into the water mains; in other cases it is 

 taken from rivers or lakes and stored in reservoirs where it is freed 

 from any sediment before being allowed to flow into the distributing 

 pipes. Sometimes certain chemicals are introduced to hasten the 

 settling of suspended matter, and in other cases chemicals are used to 

 free the water of organic matter and disease germs if any be present. 

 Some definite knowledge of the water system of one's own -city is a 

 requisite for any sufficient understanding of conditions affecting the 

 community welfare. 



Apart from the presence of disease germs, the existence in drinking 

 water of decaying organic matter, whether in a finely divided state or 

 in solution, is a source of sickness. Oxidation is the readiest means 

 of freeing water of organic matter, whether of animal or vegetable 

 nature, and whether from sewage or from decaying vegetation. 



Cistern water may be kept aerated by the use of a chain pump. 

 Running water in streams is likely to have become purified by its 

 exposure to the air, especially where its volume is not too large and 

 where its current is more or less broken. The stored water of reser- 

 voirs may be aerated by forcing air through it from pipes laid in the 

 bottom of the reservoir, or by the use of fountains whose spray of 

 water falls back into the reservoir. Where water is pumped into the 

 water mains, sufficient air for its aeration may be made to enter along 

 with the water. 



GENERAL HEALTH PROBLEMS 



The life history of flies and mosquitoes possesses great 

 interest aside from the possibility of their becoming carriers 

 of disease germs. A study of the structure and transforma- 

 tions of all insect life, and of the relations of insects to plants 

 and to mankind, is a field of science of unsurpassed interest. 

 Insects are of utmost economic importance to man, affecting 

 his health, comfort, and prosperity in innumerable ways. 



