92 



THE TREE DOCTOR 



into some people's corn or potato fields and, behold ! you could 

 not drive a crow-bar into the soil in July or August. No matter 

 how much moisture there may be in the air, how can it pene- 

 trate the ground, and condense in particles of water for the roots 

 of the plant, under such conditions? It is impossible; and the 

 crops famish. Haul a load of hot, dry sand and place it in a 

 heap on this same baked soil. Two days afterward thrust your 

 hand into it and you will find moisture. How did it get there? 

 Why, as soon as the particles cooled off, the air penetrated the 



Photo 79, Rainmakers. 



sand, and every tiny little grain became a condenser. Bring a 

 basket of potatoes out of the cellar, on a warm, spring day, and 

 in fifteen minutes they will be "sweating." "Why? They are 

 cold, and condense the moisture of the warm air. Same expla- 

 nation for the mouth of your pump "sweating" as you force the 

 cold water through it. Same answer for the "sweating" of the 

 ice-water pitcher, and all the "sweatings" on stone floors, cel- 

 lar-walls, etc. 



There is a kind of a paradox in the question of a water sup- 

 ply for crops. In heavy lands, it is absolutely necessary to take 

 the water away in order to procure a supply. That is, you take 



