1905.] 



public; DOCUMENT — No. 33. 



29 



Table VI. — Summary of Potential Readings of the Precedimj Tables, 

 showing the Total and Average Results given by Collector I. (^Free 

 Air) and Collector II. {Elm Tree). 



April, .... 

 May 1 to May 14, . 

 May 14 to May 31, 



June 



July, .... 



August 



September, . 

 October 1 to October 7, 

 October 7 to October 31, 



Total Voltage of— 



Collector 



I. — Free 



Air. 



240 

 573 



398 

 498 

 224 

 1,088 

 456 

 240 

 152 



Collector 

 II. — Elm. 



240 

 572 

 228 

 276 

 108 

 592 

 276 

 204 

 152 



Average Daily 

 Voltage of— 



Collector 



I. — Free 



Air. 



30.0 

 52.0 

 44.2 

 38.0 

 37.3 

 ,54.4 

 .57.0 

 48.0 

 19.0 



.Collector 

 II. — Elm. 



30.0 

 52.0 

 25.3 

 21.2 

 18.0 

 29.6 

 34.5 

 40.8 

 19.0 



While the results obtained from this series of experiments 

 do not possess the same value as the series extending over 

 more than one season, they nevertheless point very stronglj^ 

 to the conclusion that trees do modify to a considerable 

 extent atmospheric electrical potential in their immediate 

 vicinity. By consulting the summary, Table VI., where the 

 total and average potentials for different periods are shown, 

 it will be seen that some important differences occurred 

 between the potentials of the free air and the elm tree 

 collectors. It is significant also that there occurred no 

 difference in the readings between the free air collector and 

 that in the elm tree up to the time when the leaves developed. 

 The few readings which we were able to make in October 

 after the leaves had fallen showed the same results. 



Our interpretation of the results of these observations is, 

 that the elm tree took some electricity from the air immedi- 

 ately surrounding it during the period in which it was in 

 foliage. If this single series of observations is typical of 

 what takes place in nature, then we can conclude that the 

 atmospheric electrical potential is not affected much by trees 

 in the immediate vicinity except when they are in foliage. 

 There are a few instances where collectors I. and II. showed 



