12 ELEMENTS OF AGRICULTURE 



rates, and so long as fresh air is admitted to the room 

 so long will evaporation take place. Wind causes rapid 

 evaporation; sweeping across bodies of water, the air 

 takes up water as it goes; it is somewhat like passing a 

 dry sponge over a wet slate. Of course, the water 

 warmed by the sun does not actually boil. Water 

 evaporates when it is warmed, and the more it is warmed 

 the more rapidly it evaporates. 



6. Mist, Clouds. — Most of us have noticed on a cool, 

 frosty morning, when the sunshine strikes a pond or 

 river, how it steams like a great boiling kettle of water. 

 This is all the work of the little heat waves from the 

 sun. They evaporate the surface water, which, rising 

 into the cool air, is condensed into tiny drops of water, 

 which form mist.. Mist, then, is made up of very small 

 drops of water. Mist, or fog, as it is sometimes called, 

 rises high above the earth and gathers into what we call 



CLOUDS. 



7. Rain. — Clouds which we see floating about in the 

 air are still warm from the sunshine which helped to 

 form them. When they come in contact with a cold 

 current of air, or a cold mountain top, they lose this 

 heat and condense to drops of water, which being 

 heavier than air fall as rain. The cold air or mountain 

 top acts just as any cold body would if held in a cloud 

 of steam. 



8. Hail, Snow. — Sometimes raindrops are caught in 

 very cold currents of air. In these air currents they are 

 held till they become balls of ice, in which form they 

 fall as hail. When the air becomes sufficiently cold, 



