114 ELEMENTS OF GENERAL SCIENCE 



What is the normal temperature of a healthy person? Try 

 your own temperature by placing the bulb of a thermometer 

 under your tongue. 



127. Amount of water evaporated by the air. When we 

 consider that the oceans, lakes, and rivers make up the larger 

 part of the surface of the earth, and that water is evaporating 

 from this surface all the time, it is plain that a very large 

 amount of water evaporates. How much it is, no one knows 



FIG. 61. Rate of evaporation in the United States 



The map shows the estimated rate of evaporation in inches per annum. Note the 

 great differences between different parts of the country. After Cox 



exactly, but we get some idea when we remember that all of 

 the water that falls as rain or snow has evaporated somewhere 

 most of it from the ocean, but some of it from the land. 



A study has been made of the rate of evaporation in the 

 United States (fig. 61), and it is believed that about 30 inches 

 of water evaporates each year from the surface of Lake Michi- 

 gan, and about 70 inches from the Great Salt Lake ; in some 

 of the desert regions of the Southwest perhaps as much as 

 100 inches would evaporate annually if there were any body 



