CLIMATIC CONDITIONS OF THE UNITED STATES. 



315 



The evaporation-rates are here shown to have been rather uniform, 

 on the whole, with a suggestion of a 3-week periodicity. 



Easton, Maryland (fig. 11): Here the weekly rates of evaporation 

 varied from a minimum value of 59 c.c. (weeks ending August 31 and 

 November 2) to a maximum of 308 c.c. (week ending June 20). There 

 occurred a general rise in these rates from the beginning of the series 

 to about July 20, after which the evaporation intensity was low and 

 strikingly uniform. It is interesting to note that the highest rate for 

 Easton is higher than any rate encountered in the sunmaer rainy season 



FiQ. 9. — Weekly precipitation and evaporation indices, summer of 1908, MacDonald College, 



Ste. Anne de Bellevue, Quebec. 



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 Fig 10. — Weekly precipitation and evaporation indices, summer of 1908, Orono, Maine. 



at Tucson, and the three highest for Easton are higher than any rate 

 experienced at San Diego during the whole series of observations at 

 that station. Curiously enough, the two graphs for Easton are similar 

 in their general form to those for Tucson. In both cases a fore-sum- 

 mer of low rainfall and of generally increasing evaporation intensity 

 is finally broken by a heavy rain, which ushers in a period of greater 



