DISCUSSION. 27 



by evaporation. I recall a specific illustration in the San Ber- 

 nardino Mountains. Before the mountains were lumbered a 

 stream near the summit of the range was perennial in its flow. 

 In recent years the middle area through which the stream 

 runs has been lumbered and burned. At present the stream 

 keeps up its flow until it reaches the denuded and burned area, 

 when it entirely disappears, but as soon as the stream reaches 

 the wooded area again it reappears. 



Dr. ROTHROCK. That shows the enormous amount of 

 evaporation which takes place. When I was in Arizona, 

 which, of course, is an exceedingly dry country, I saw some 

 illustration of that. It shows the wonderful power of the sun 

 to take up or absorb the precipitation there, which is prin- 

 cipally in the month of June. 



Mr. HINMAN. Mr. Hale is not here to combat this theory, 

 but he told us yesterday if we wanted to hold the moisture in 

 our orchards we must not set too many trees. And that if the 

 trees were set so that they covered the ground too closely, 

 they absorbed the moisture, and that the crop was ruined. 

 He said that in a dry season it was better to have fewer trees, 

 because the evaporation from the soil was nothing like as 

 great as the evaporation that the trees threw off through being 

 set closer together. 



Professor TOUMEY. I think if you were to put out your 

 orchards and not attempt to cultivate them at all you would 

 find that your trees would die from lack of moisture. In your 

 orchards you conserve the moisture in the soil by cultivation; 

 in the forest the soil moisture is conserved by the mulch. If 

 trees are too far apart no mulch will be produced. I admit 

 if you produce a soil mulch by cultivation, the greater the 

 number of trees upon a given area, the greater will be the 

 loss of moisture through transpiration. 



Secretary GOLD. I must beg leave to cut this interesting 

 discussion off at this moment that I may introduce to you a 

 man whom you will all be glad to hear, Professor Ballou of 



