AGRICULTURAL EXPERIMENT STATION. 143 





HYGROMETER 



NO. 4 



IN FOREST. 









1889. 



1890. 



1889. 



1890. 



1889. 



1890. 







7 A. M. 



7 A.M. 



1P.M. 



1 P. M. 



7 P.M. 



7 P. M. 



Menu 



April, 



83 



79 



65 



60 



77 



71 



72 



May, 



89 



S8 



66 



73 



80 



84 



80 



June, 



92 



89 



81 



77 



86 



84 



85 



July, 



93 



91 



79 



79 



87 



85 



86 



August, 



95 



91 



S6 



78 



91 



85 



88 



September, 



96 



97 



83 



86 



90 



92 



91 



October, 



96 



94 



80 



80 



90 



S9 



88 



Mean results, 92 90 77 76 86 84 SI 



Percentages of Moisture, 

 results for 1889 and 1890 combined. 





7 A.M. 



1P.M. 



7 P.M. 



Mean 



ygrometer No. 1, in open field. 



87 



65 



76 



76 



l. 2 , »• " » 



83 



61 



72 



72 



•' •' 3. in forest, 



90 



79 



84 



84 



k . 4 ,. ,. 



91 



76 



85 



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. IP. M. 7 P.M. Mean. 

 Percentages of moisture, open field, 85 63 74 74 



Regarding the mean results from hygrometers No. 3 and 4 as 

 indicating percentages for forests only moderately dense, we have 

 the following summary results : 



7 A. M. 1 P. M. 7 P. M. Mean. 

 Percentages of moisture, forest, 90 7S 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. IP. M. 7 P.M. Mean. 

 5 15 10 10 



It thus appears that from observations covering the period of 

 growth of two years, that the excess of moisture in forest above 

 that of open field in the morning, amounts to but 5 per cent., 

 while in the middle of the day it rises to 15 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. 



