6o 
JOHN H. EHLERS 
ture is due, no doubt, to a difiference in intensity of insolation, column 7 
of Table IV showing slightly higher values than the corresponding 
columns in Tables VI, XII and XIII. But the difference in the 
intensity of insolation is slight and can account for only a small part 
of the reduction. The wind, therefore, is the important factor. 
Table XII 
February i, IQ14 
Clear. Strong wind.^ Relative humidity 71% 
Time of 
Obser- 
vation 
12.35 
12.45 
1.50 
1.58 
No. of 
Obser 
vations. 
Bridge 
Readings 
in Cm. 
17.4 
22.1 
27.0 
23.8 
Average 
Computed 
Temp. 
DifF. 
2. II 
2.68 
3.28 
2.89 
2.74 
Shade 
Temp. 
-3.0 
-31 
-3-5 
-3-2 
-3-2 
28.6° 
29.0 
29.2 
20.0 
Diff, 
Columns 
5 and 6 
31.6° 
32.1 
32.7 
23.2 
29»9 
Actual 
Leaf 
Temp . 
— 0.42 
— 0.22 
-0.31 
— 0.46 
Wind 
Vel. 
Miles 
per Hr. 
ty 
6.0 
6.0 
6.0 
4.8 
March 2, IQ14 
Relative humidity of 90% 
I 
2 
3 
4 
5 
6 
7 
8 
9 
8.52 
7 
15.4 
1.91° 
— 12.2° 
9.4° 
21.6° 
10.29° 
4.8 
9-36 
4 
17.1 
2.12 
-11.3 
21. 1 
32.4 
9.18 
4.8 
10.06 
8 
23.0 
3.83 
- 8.5 
27.2 
35.7 
4.67 
5-0 
11.00 
20.0 
2.46 
6.04 
3-6 
10.5 
1.29 
7.21 
7.5 
•92 
7-58 
22.6 
2.78 
5.72 
26.5 
3.26 
5-24 
13.2 
1.62 
6.88 
19.0 
2.34 
6.16 
7.0 
.86 
7.64 
22.5 
2.77 
5.73 
39.3 
4-83 
3.67 
11.05 
28.0 
3.44 
5.06 
12.31 
8 
16.8 
2.06 
- 6.5 
26.1 
32.6 
4.44 
4.8 
Average 
2.61 
- 9.4 
31.6 
6.93 
The effect of gusts of wind is shown in the rapid fluctuations in 
the differential temperature for the period ii.oo to 11.05, Tables IV 
and XIII. Fluctuations of 2° and 3° C. occur within one half minute. 
^ Wind velocity, University Observatory record, Feb. i, 15 miles per hour; 
March 2, 26 miles per hour. 
