THE TEMPERATURE OF LEAVES OF PINUS IN WINTER 
49 
Table II 
Temperature 
Date 
Displacement 
Calculated Temp. 
Error 
Actual 
DifF. in Deg. Cent. 
A 
B 
Dec. 27 
24-53° 
18.38° 
6.15° 
53-2 
6.149 
0.001 
24.52 
18.39 
6.13 
52.9 
6.II5 
0.015 
26.25 
18.40 
7-85 
68.3 
7-895 
0.045 
24.65 
18.85 
5.80 
50.2 
5-803 
0.003 
24.62 
18.85 
5-77 
49.8 
5-757 
0.013 
23-35 
4-45 
38.6 
4.462 
0.012 
23-32 
18^93 
4-39 
38.0 
4-392 
0.002 
Dec. 28 
20.21 
18.04 
2.17 
18.8 
2.173 
0.003 
21.86 
18.02 
3-84 
33-2 
3.838 
0.002 
19.19 
18.16 
1.03 
8.9 
1.029 
O.OOI 
19-13 
18.15 
-98 
8.5 
.983 
0.003 
Jan. 5 
8.00 
0.00 
8.00 
66.7 
8.037 
0.037 
5-00 
0.00 
5-00 
41.6 
5.013 
0.013 
2-97 
0.00 
2.97 
24-7 
2.976 
0.006 
Jan. II 
-7.40 
-14.68 
7.28 
58.4 
7.293 
0.013 
-7.18 
-14.70 
7-52 
60.4 
7-543 
0.023 
-7-05 
— 14.00 
6.95 
55-6 
6.950 
0.000 
-9.25 
— 16.67 
7.42 
58.7 
7-365 
0.055 
-9.80 
-17.03 
7-23 
57-3 
7.198 
0.032 
-5-05 
— 10.00 
4-95 
39-9 
4.924 
0.026 
1 Average error 
0.0155 
Mar. 22 
4-15 
0 
4-15 
34-2 
4.118 
0.032 
4.18 
0 
4.18 
34-8 
4.190 
0.010 
4.28 
0 
4.28 
35-7 
4.298 
0.018 
4-38 
0 
4-38 
36.4 
4-383 
0.003 
4-45 
0 
4.45 
36.6 
4.406 
0.056 
4-56 
0 
4-56 
37-9 
4-563 
0.003 
4-77 
0 
4-77 
39-7 
4.789 
0.019 
5.18 
0 
5-18 
42.8 
5.153 
0.027 
5-34 
0 
5.34 
44-2 
5-322 
0.018 
5-45 
0 
5-45 
45-0 
5.418 
0.032 
5-50 
0 
5-50 
46.0 
5-538 
0.038 
'Average error 
0.0233 
formation of secondary couples; (3) heat due to wounding of the leaf 
tissue; (4) loss of heat by conduction along the lead wires. 
(i) Variation of the Current from the Cell. — To guard against any 
variation of the current from the cell, a Weston voltmeter and a 
rheostat were connected across the terminals of the potentiometer 
circuit as already described. The simple throwing of a switch enabled 
the operator to detect any change in the voltage applied to the poten- 
tiometer circuit. Corrections could then be made by varying the 
resistance of the rheostat. 
