100 WATER 



trations, from thick paper, folding: on the dotted lines, 

 and pasting their edges together by means of strips of 

 paper. 



38. Water for Drinking. 



There is hardly any pure water as it occurs in nature. 

 On account of the great power which water has to dis- 

 solve so many substances, there is usually some material 

 held in solution. Fortunately for us, many of the sub- 

 stances found in water are not harmful to man, while 

 some of them are very helpful. The harmful substances 

 which are dissolved in water are usually so bad tasting 

 that there is little danger from them, for no one will drink 

 the water. 



While the dissolved material is usually harmless, 

 there is great danger in drinking impure water. This is 

 due to a kind of plant life we have already become 

 acquainted with in Sections 13 and 25. Some of these, 

 which we learned were called bacteria, may cause typhoid 

 fever. Although the water is clear and seems pure, the 

 bacteria may be present. On the other hand, dirty 

 water may be free from bacteria and be harmless. Wells 

 should be so located that drainage cannot possibly reach 

 them, for decayed animal matter is what these bacteria 

 live upon. Since water can pass through the porous 

 rocks, wells must be far away from open drains and 

 stables. 



The body requires a large amount of water and most 

 grown persons do not drink enough. The more water 

 we drink the better are the wastes carried from the body. 

 We have learned that while water can dissolve many 



