IV. WATER 



WATER is composed of two substances, hydrogen and oxygen, 

 in the proportion of two volumes of the former to one of the latter. 

 A fresh living plant consists largely of water. Young grass and 

 fresh potatoes are about three fourths or 75 per cent water, which 

 may be driven off by continuous heating to 212 F., the boiling 

 point of water under normal conditions. Beets and carrots contain 

 from 80 per cent to 90 per cent of water. They are constantly 

 absorbing water through their roots and giving it off through 

 their leaves. Carefully conducted experiments show that for 

 every pound of dry matter in oats three hundred and seventy-six 

 pounds of water are required, three hundred and thirty-eight pounds 

 for wheat, and three hundred and ten for red clover. If we assume 

 that about 80 per cent of clover is water, we can easily calculate 

 how much water would be used up in growing ten acres of clover 

 weighing about twelve thousand pounds. Trees as a rule contain 

 less than one third their weight of water. This percentage in- 

 creases during the spring and decreases slightly in the winter. The 

 amount also varies for different trees. From monthly determi- 

 nations it has been found that the average yearly amount of water 

 in a pine tree is 61 per cent, in a poplar 53 per cent, in a birch 

 49 per cent, and in a maple 42 per cent. 



Water is one of the most abundant substances found on the earth. 

 Curiously enough we find here, as in the case of plants, that about 

 three fourths of the earth's surface is composed of water, while only 

 one fourth is land. Water is also present in the air in the form 

 of vapor. The amount, which we call humidity, varies greatly 

 in different parts of the United States. In the States along 

 the Gulf Coast and a narrow belt along the sea in Oregon and 

 Washington, the humidity is great and the rainfall is from fifty 

 to sixty inches. On the other hand there are districts in Nevada, 

 Arizona, and Utah where the rainfall is less than five inches a year. 

 The explanation is found in the fact that the moist air from the 



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