AGRICULTURAL EXPERIMENT STATION. 151 



Percentages of Moisture, 

 results for 1889, 1890, 1891 and 1892, combined. 









7 A. M. 



I p. M. 



7 P. M. 



Mean 



Hygrometer 



No. 1, 



in open field. 



86 



64 



75 



75 



(( 



" 2, 



(( a u 



84 



62 



73 



73 



u 



" 3, 



in forest, 



90 



78 



84 



84 



(( 



" 4, 



U li 



91 



76 



84 



84 



Regarding the mean results from hygrometers Nos. 1 and 2 as 

 indicating percentages for the open field, we have the following 

 summary of results : 



7 A. M. I p. M. 7 p. M. Mean 



Percentages of moisture, open field, 85 63 74 74 



Regarding the mean results from hygrometers Nos. 3 and 4 as 

 indicating percentages for forests only moderately dense, we have 

 the following summary results : 



7 A. M. I P. M. 7 P. M. Mean 



Percentages of moisture, forest, 91 77 84 84 



Comparing results, open field and forest, we have excess of 

 moisture in forest above that in open field expressed in percent- 

 ages. 



7 A. M. I P. M. 7 P. M. Mean 



6 14 10 10 



It thus appears from observations covering the period of 

 growth of four years, that the excess of moisture in forest 

 above that of open field in the morning, amounts to but 6 per 

 cent., while in the middle of the day it rises to 14 per cent., 

 and at night-fall drops down to 10 per cent., and that the 

 mean excess for the day is 10 per cent. In a very dense forest 

 the percentage of excess would undoubtedly rise much 

 higher. The presence of patches of forest in any region 

 exerts a marked influence on the hygroscopic conditions of 

 the atmosphere, and this condition, in turn, is an important 

 factor in the growth of vegetation. 



