CHAPTER V 



WATER 



79. How Water Occurs in Nature. We commonly 

 think of water as a clear, easily poured liquid; we must 

 also think of it as a solid: snow, frost, and ice, and as a 

 gas or vapor: steam. Water is very abundant, not only 

 in rivers, lakes, and the ocean, but also in the earth's 

 solid crust. No matter where we dig, we find it even in 

 the desert. The atmosphere likewise contains a great 

 deal: as steam. Water makes up a large part of all plants 

 and animals. The following table shows how much of 

 our bodies and our food is water: 



Human body 70% Watermelon 92% 



Milk 87% White bread 35% 



Potatoes 78% Beef 62% 



Natural water is never pure. The rain gathers material 

 from the atmosphere (cf. 58) ; the water that flows over 

 or through the earths crust dissolves substances from 

 the soil and the rock; and both rain and running water 

 take up living creatures, such as bacteria (cf. 56 and 

 324). Rivers and lakes become impure because of the 

 sewage, or waste matter, of the cities, factories, and farms 

 upon their banks. 



The purest natural water is probably obtained by melt- 

 ing some ice obtained from a pure source. 



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