WATER AND 

 LAND 



ICEANS are the earth's 

 great storehouse of water. 

 They cover some eight- 

 elevenths of the surface 

 of the earth to an average 

 depth of about two miles. 

 They receive the off-flow 

 from all the continents 

 and send it back by way 

 of the atmosphere. 



The fresh waters of the earth descend in the first 

 instance out of the atmosphere. They rise in vapor 

 from the whole surface of the earth, but chiefly from 

 the ocean. Evaporation frees them from the ocean's 

 salts, these being non- volatile. They drift about with 

 the currents of the atmosphere, gathering its gases to 

 saturation, together with very small quantities of drift- 

 ing solids; they descend impartially upon water and 

 land, chiefly as rain, snow and hail. 



They are not distributed uniformly over the face of 

 the continents for each continent has its humid regions 

 and its deserts. Rainfall in the United States varies 

 from 5 to 100 inches per annum. Two-thirds of it 

 falls on the eastern three-fifths of the country. For the 

 Eastern United States it averages about 48 inches, for 

 the Western United States about 12 inches ; the average 

 for the whole is about 30 inches. The total annual 

 precipitation is about 5,000,000,000 acre-feet.* 



*An acre-foot is an acre of water i foot deep or 43,560 cubic feet of water. 



55 



