96 



water level of the streams. Rut his i-epdrt has been shown to be so fu!. 

 of glariuir inac-curacies ami iiiisstatciiients that its conchisions are almost 

 wholly discredited by scientific mci!. (12), (29), and (38.) 



Other literature, uuich of which has contributed nothing new to the 

 subject, has In^n gone over and after considering all the facts it may be 

 safely said that the weight of evidence seems to show that forests do in- 

 crease precipitation, at least to a small extent. 



Evaporation. 

 Under the best of conditions much of the precipitated water is lost 

 by evaporation. The proportion evaporated varies greatly in different parts 

 of the world and under different conditions of season and soil. It de- 

 pends principally on the temjierature, the wind, and the amount of moist- 

 ure already in the air. That the forest retards evaporation cannot be 

 denied. The shade which it affords the soil and its relatively cooler tem- 

 perature in summer retards evaporation to a great extent. The greater 

 amount of moisture in the atmosphere of the forest is another factor which 

 reduces evaporation. Winds are checked by the forest and their ix)wer 

 to take up moisture limited. The wind and sun in winter evaporate a 

 great portion of the snowfall. In the San Bernardino Mountains, snow- 

 falls a foot in depth are frequently evaporatetl in two or three days with- 

 out even moistening the soil. The forest aids in reducing tliis lo.ss in so 

 far that it furnishes shade and checks the wind. Experimt>nts in Ger 

 many have proved that evaporation under trees is about one-half of that 

 ill tile open and show a saxiiii,' of 21 per cent, of the i(re(i]iitatioii by the 

 woods. The evaporation and saving by the forest were both greatest i:i 

 May and June. It was also found that deciduous trees when in leaf re 

 tarded evaiioiatinn UK.re than the evergreens and that evaporation under 

 young trees was only 20 per (cut. less than in the open. t\)llowlng is 

 data from a series of investigations by Dr. Ebermayor and by German in- 

 vestigators : 



