1905.] 



PUBLIC DOCUMENT — No. 33. 



21 



the bi-aiichcs and leaves. The tree, however, Avas not in 

 every respect a typical ehn for this region, the head being 

 high and close, with the branches drooping but little. 



Tlie collector in the tree is designated as II. in tlie follow- 

 ing monthly records ; and the one in the free air, which was 

 located near a building, is designated as I. Collector III. 

 was in a spruce tree, and Nos. IV. and V. were added in 

 August. Collector III. was located 12 feet high, near the 

 top and under the branches of a small Norway spruce. Nos. 

 IV. and V. represent readings from two small Norway spruce 

 trees, about 2 feet high, in pots ; they were located about 

 16 feet from the ground, on a plank scaffold. No. IV. had 

 a copper plate in the soil, w^hich was connected with the 

 electrometer when readings were made. No. V. had a sim- 

 ilar plate, but was grounded with an insulated wire ; another 

 wire led from this copper plate in the soil to the electrom- 

 eter. 



Readings were taken from the various collectors on the 

 same electrometer at practically the same time each day. 

 Table V. shows readings taken from April 20 to Nov. 1, 1904, 

 and where readings are omitted they could not be obtained. 

 All readings not otherwise recorded imply negative potential. 



Table V. — Records showing the Electrical Potential (Volts) taken from 

 an Elm Tree and from Free Air. 



