206 Introduction to the Study of Science 



24. What difficulties are encountered in building dams? 25. De- 

 scribe one of the notable dams built by the United States Reclamation 

 Service for irrigation and power purposes. 26. What is the estimated 

 acreage of land available for reclamation by irrigation? In what 

 states is this land located? 



SUGGESTIVE QUESTIONS 



1. Which needs the more water for drinking purposes, a man or a 

 horse? Which makes use of the larger amount? Why? 2. Give 

 reasons for the greatly increased consumption of water in recent 

 years. 3. If you live in the country, find out the average depth of 

 wells in your vicinity; the character and sufficiency of the water 

 supply throughout the year ; and the safety of the water as indicated 

 by the location of the wells relative to drainage. 4. Through what 

 kind of ground are the wells sunk? 5. If you live where artesian 

 wells are found, ascertain depth of wells, source, and distance of wells 

 from source ; character of water as hard or soft. 6. If you make use 

 of cistern water, how can you make it safe for all purposes? 7. Why 

 do certain rivers of the central western states disappear largely or 

 wholly during the dry season? 



V. THE WATER SUPPLY AND DISEASE 



81. Water as a carrier of disease germs. Water is gen- 

 erally considered a means of distribution of several kinds of 

 disease germs. What evidence is there to support this opinion? 

 The chief questions to be considered in this chapter are the 

 following. Is water a suitable means for carrying disease 

 germs? How do such germs come into water commonly 

 considered safe? Or is water, as we find it in nature, unsafe 

 for drinking? 



The most familiar diseases considered as water-borne are 

 typhoid fever, dysentery, and cholera. These have become 

 associated in the minds of many people with the water supply. 

 An epidemic of typhoid fever, for example, now raises specific 

 questions as to the carrier. Is it the water polluted by sewage? 

 Is it the milk supply, unclean food, or the house-fly? In every 

 case investigation soon eliminates all but one or two possible 



