1912.1 



PUBLIC DOCUMENT — No. 31. 



173 



to March 20, and were made at 8 a.m., 12 m. and 6 p.m. each 

 day. Corresponding air temperatures were made for the same 

 period. These observations were made with centigrade ther- 

 mometers, which were carefully protected from external influ- 

 ences. We transposed their readings into Fahrenheit and found 

 that the average temperature given by the south side of the tree 

 was 31.43° F., while that for the north side was 30.57° F. The 

 air temperature for the same period, as might be expected, was 

 variable, averaging slightly higher than that for the inside of 

 the tree. 



The average temperature readings obtained by Jones, Edson 

 and Morse from the north and south sides of the tree showed 

 that the temperature on the north side was about 3 per cent, 

 lower than on the south side. The average obtained from all 

 our electrical resistances and temperature readings are given 

 below in sequence : — 



Average 

 Electrical 

 Resistance. 



Average 

 Temperature 



of Trees 

 (Degrees F.). 



North side. 

 West side, 

 South side. 

 East side. 



27,081 

 25,714 

 25,566 

 23,708 



30.91 

 32.14 

 33.60 

 32.28 



It will be noticed that the highest average resistance of trees 

 was given by the north side, followed by the west, south and east 

 sides, and this sequence was closely followed by the temperature 

 readings, the lowest being given 'by the north, followed by the 

 west, east and south sides. The temperature readings lasted 

 seven days only, and were too incomplete to obtain a true aver- 

 age. It will be noticed, however, that there was a difference 

 of about 8 per cent, between the resistance of the east and west 

 sides of the tree, a feature which would result from the greater 

 intensity of the morning light. In our temperature readings, 

 which are probably not as good averages as those obtained by the 

 authors noted above, we find that the north side of the tree 

 showed a temperature equal to 7 per cent, lower than the south 

 side, as compared with 3 per cent, given by Jones, Edson and 



