51 
DATE. 
Exposed Black 
Bulb Therm, 
on Grass. 
Exposed Black 
Bulb Therm. 
6 feet from 
ground. 
Difference. 
Black Bulb 
Therm. 
in vacuo 
on grass. 
Difference 
from Therm. 
6 feet 
from ground. 
1867 
o 
o 
o 
o 
o 
Oct . 
1 
692 
73-0 
+ 3-8 
83-2 
4 - 10-2 
2 
575 
576 
- j - 01 
62-1 
4- 4-5 
3 
61-4 
627 
+ 13 
710 
4- 8-3 
4 
52-5 
57-0 
4- 4 - 5 
600 
4- 3 0 
5 
665 
68-2 
+ 17 
72-2 
-f 4 0 
6 
640 
680 
4 0 
67*7 
— 0-3 
7 
60-7 
67*2 
4 - 6-5 
77-4 
4 - 10-2 
8 
54*9 
60-1 
4- 5-2 
68-0 
■ -h V-9 
9 
46-7 
45*8 
— 0-9 
48-9 
4 - 31 
10 
620 
67-6 
+ 5-6 
75-8 
4 - 8-2 
55 
11 
51-3 
525 
+ 12 
54-0 
4 - 1-5 
55 
12 
56-2 
56-5 
4- 0-3 
56-5 
o-o 
55 
13 
53-4 
52-7 
— 07 
57-0 
4- 4-3 
55 
14 
60-0 
61*5 
+ 1-5 
61*2 
— 0 3 
55 
15 
61*0 
636 
+ 2-6 
65-0 
+ 1-4 
55 
16 
64-8 
74-3 
+ 95 
71-0 
— 3-3 
55 
17 
63-0 
74-8 
+ 11*8 
71*1 
— 3-7 
18 
62-5 
70-7 
+ 8-2 
675 
— 3-2 
19 
57*3 
68-2 
+ 10-9 
62-0 
— 6-2 
20 
60-5 
68-9 
4- 8-4 
64-4 
— 4-5 
55 
21 
60-0 
63-8 
-b 3-8 
63-1 
— 0-7 
22 
72.8 
82*1 
4" 9 3 
79-8 
— 2-3 
55 
23 
64-0 
64-8 
4- 0-8 
65-6 
+ 0-8 
55 
24 
• 54-2 
55-4 
+ 1'2 
56-0 
4 - 0-6 
55 
25 
51-8 
525 
4 - 0-7 
53-0 
4- 0-5 
26 
62-0 
69-3 
4- 7-3 
65-3 
— 4-0 
5) 
27 
50-3 
51-4 
4- i-i 
53-7 
4 - 2-3 
55 
28 
52-6 
61-9 
4“ 9 3 
58-7 
— 3-2 
29 
59-4 
654 
4 - 6-0 
62-0 
— 3-4 
55 
30 
61*0 
68-8 
4- 7-8 
670 
— 1-8 
55 
31 
58-3 
64-8 
4- 6-5 
64-2 
— 0-6 
Mean . . . 
590 
62-9 
- f - 3-9 
64-6 
4 - 1-7 
It appears therefore that, for the month, at a position six 
feet above the ground, there is a mean difference of solar 
influence of nearly 4 degrees above that upon the grass; and 
in some extreme instances the difference has been from 10 
to nearly 12 degrees. A thermometer placed in vacuo on 
the grass has only exceeded this difference by T7 degree. 
These results show how important it is that some definite 
principle should be adopted in the placing of solar thermo- 
meters, as certainly no comparison can be made between the 
amount of solar radiation at any two or more places, unless 
some common plan of placing the instruments be adopted. 
