146 



EXPERBIENT STATION. 



[Jan. 



Table II. — Showing Daily Records of Electrical Resistance (in Ohms) of 

 Elm (Ubnus Americana, L.), April 7-26, 1907. Resistances taken 

 on the North, South, East and West Sides of the Tree at Midday. 



[Electrodes 10 feet apart. Mean tlaily temperatures given in degrees F.] 



Date. 



Tempera- 

 ture. 



East. 



South. 



West. 



North. 



The data shown in Tables I. and II. give the electrical resist- 

 ance of a maple and elm tree covering a period of nearly one 

 month in the spring, when there was an occasional flow of sap. 

 The elm was a large tree, over 2 feet in diameter, and the maple 

 was nearly as large. In both eases the electrodes, which were 

 about 3 inches long and made of galvanized iron nails, were 

 driven through the bark and into the wood. These were con- 

 nected by solder with insulated copper wires leading to a com- 

 bination In-idge, from which the readings w^ere made. The 

 batteries consisted of half a dozen cells employed to take the 

 readings. In these experiments the electrodes were 10 feet 

 apart on the north, south, east and west sides of the trees. The 

 lowest electrodes were placed about 2 feet above the ground, and 

 the highest about 12 feet. 



' Warm. 



