EVAPORATION 



with moisture moves aside to let air containing less moisture take 

 its place, more of the water on the wet object is evaporated. 



Other Ways in which Moisture Gets into the Atmosphere. 

 All animals breathe out water vapor into the atmosphere. A 

 person will give off to the atmosphere each day, by perspiration 

 and respiration, from a pint to three quarts of water, according 

 to the amount of exercise taken. Plants give out large quantities 

 of water. A sunflower will give off from a pint to a quart of water 

 each day, or about 125 pounds of water during the season. 



An average oak tree gives off about 200 gallons of water 

 in a day during the summer. A birch tree with about 200,000 

 leaves has been estimated to give off from 700 to 900 pounds of 

 water, or about 125 gallons, on a hot day in summer, and only 

 about two or three gallons on a cool day. In hot weather an acre 

 of grass will give off enough water to the atmosphere to equal its 

 own weight, or about 1600 gallons a day. This would mean about 

 six and a half tons of water or a little more than 50 barrels. An 

 average sized city lot covered with grass will give to the atmosphere 

 about 10 barrels of water on a hot day. This means that if our 

 lawns are well kept they will give off water vapor in large quantities. 



Evaporation from the Soil. 

 Large amounts of water 

 evaporate from the soil, but the 

 amount depends upon the con- 

 dition and kind of soil. More 

 water evaporates from soil 

 which is full of tiny openings 

 (fine porous soil) since the 

 water rises to the surface more 

 rapidly in such soil than in soil 

 which is very loosely packed 

 together. 



A farmer cultivates his gar- 

 den frequently during warm weather in order to form a dust mulch 

 an inch or so thick. The water will rise in the soil up to the dry 

 layer, and the greater part of the water will be absorbed by the 

 roots of the plant. This process is called " dry farming." Rolling 



FIG. 2. 



