1912.] PUBLIC DOCUMENT — No. 31. 169 



obtained in Table I., the curve being based on daily readings 

 on the north, south, east and west sides of the tree. All of these 

 figures show that there exists a marked relationship between the 

 temperature curve and that for the electrical resistance, since 

 as the temperature curve goes up the resistance curve goes down. 



58°F 



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48 

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 44 

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52 



30 



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27 

 2 6 

 25 

 24 

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APR. 



FiQ. 1. ^ Showing curve of electrical resistance and temperature of elm, Ulmus Americana 

 (Table II.). The lower curve gives the average resistance of the north, south, east and west 

 sides of the tree from April 6 to 26; the upper curve gives the mean of the minimum and max- 

 imum temperature for the same period obtained from the local meteorological station. 



In Fig. 3 is shown the hourly temperature and electrical 

 resistance of the north side of a maple tree for a single day, the 

 data being obtained from Table IX. In both Figs. 1 and 2 the 

 temperature is taken from mean temperature records, while in 

 the case of Fig. 3 they correspond with the hours of observation. 



