no 



THE PLANT WORLD 



evaporating power of the air. In the last column are similar 

 averages of the weekly losses from the instruments, for the 

 entire period of seventeen weeks. The stations are arranged 

 in the order of the magnitude of the quantities in the last 

 column. All these data may be reduced to millimeters of 

 depth of evaporation from a free water surface, by dividing 

 each by the number 6, for it was found that a loss of six 

 cubic centimeters from this instrument corresponds, approx- 

 imately, to a loss of one millimeter evaporated from an open 

 vessel. 



Relative Evapurating Power of the Air at 

 United States, June 3, to September 



16 Stations in the 

 30, 1907. 



Average for i:; w hi 



iiisU-ul "I IT, 



From the table it is seen at a glance that the evaporating 

 power of the air was much greater in the arid Southwest 

 than in any other portion of the region under observation. 

 It is also evident that the stations exhibiting the least evapora- 

 tion are on the Great Lakes or Atlantic Seaboard. A number 



