196 
MR. GLAISHER ON THE RADIATION OF HEAT. 
Table XCIX. — Mean Monthly excess of the readings of the thermometer in Air above 
that in the Reflector. 
General state of the sky 
during the night previous 
to reading the instru- 
| ments. 
Month. 
The mean monthly excess, according to the state of the sky with respect to the quantity of cloud, of the readings 
of a self-registering thermometer placed in air at the height of 4 feet and protected from radiation, above those 
of a similar thermometer placed in the focus of a metallic parabolic reflector. 
1841. 
1842. 
1843. 
1844. 
1841 Feb. 10, to 1844 Dec. 31. 
Mean 
excess. 
No. of 
nights. 
Mean 
excess. 
No. of 
nights. 
Mean 
j excess. 
No. of 
nights. 
Mean 
excess. 
No. of 
nights. 
No. of 
nights. 
Sum of 
excess. 
Mean 
excess. 
Cloudless. 
January. 
• 
9’4 
6 
9-5 
8 
o 
8-0 
2 
16 
148-7 
9-3 
February. 
5-8 
i 
8-1 
4 
110 
5 
70 
4 
14 
121-4 
8-7 
March. 
71 
12 
6-5 
8 
10-2 
15 
6-5 
7 
42 
336-2 
8-0 
April. 
9-4 
7 
71 
9 
101 
11 
8-0 
18 
45 
384-9 
8-1 
May. 
7-2 
7 
8-5 
8 
10-5 
2 
81 
10 
27 
219-7 
8-1 
June. 
8-8 
4 
102 
12 
10-3 
7 
6-8 
6 
29 
267-5 
9-2 
July. 
7-4 
4 
8-7 
6 
10-1 
2 
8-2 
12 
24 
199-9 
8-3 
August. 
9-9 
4 
6-2 
11 
91 
6 
71 
12 
33 
247-6 
7-5 
September. 
8-1 
6 
4-5 
3 
9-2 
11 
9-7 
12 
32 
279-0 
8-7 
October. 
8-7 
5 
. 91 
9 
6-6 
8 
6-8 
8 
30 
2277 
7-6 
November. 
81 
9 
10-6 
3 
8-5 
6 
60 
2 
20 
167-7 
8-4 
December. 
8-7 
7 
6-6 
6 
0 
9-3 
6 
19 
156-0 
8-2 
Principally cloudless. 
January. 
6-2 
7 
7-3 
3 
4-6 
7 
17 
97-2 
5-7 
February. 
0 
5-8 
5 
7-2 
2 
5-5 
6 
13 
76-5 
5-9 
March. 
6-1 
5 
6-6 
3 
8-4 
5 
4-9 
2 
15 
101-6 
6-8 
April. 
5-8 
6 
51 
7 
7-4 
6 
7-4 
4 
23 
144-4 
6-3 
May. 
7-0 
4 
6-7 
10 
7-8 
4 
60 
5 
26 
179-7 
6-9 
June. 
7-4 
6 
6-4 
8 
7-6 
6 
7-7 
5 
26 
187-6 
7-2 
July. 
4-7 
3 
6-5 
13 
8-4 
10 
71 
1 
26 
180-9 
6-9 
August. 
5-6 
6 
5-7 
4 
8-1 
12 
7-5 
6 
28 
198-2 
71 
September. 
5-5 
4 
5-7 
9 
9-2 
11 
8-6 
5 
24 
169-1 
7-0 
October. 
7-0 
1 
6-7 
8 
6-6 
8 
6-8 
6 
23 
157-7 
6-9 
November. 
7-2 
2 
7-5 
11 
71 
7 
8-1 
7 
28 
210-7 
7-5 
December. 
71 
5 
6-2 
6 
6 1 
5 
8-2 
1 
18 
111-3 
6-2 
Half-cloudy. 
January. 
5-8 
7 
60 
6 
4-4 
5 
18 
96-8 
5-4 
February. 
3-2 
i 
3-6 
7 
8-4 
5 
3-7 
6 
19 
106-7 
5*6 
March. 
5-1 
5 
4-2 
11 
7-3 
3 
4-4 
9 
28 
132-9 
4-7 
April. 
5-6 
6 
4-8 
8 
5-3 
8 
3-4 
3 
25 
125-4 
5-0 
May. 
5-1 
6 
61 
5 
5-1 
4 
5-9 
6 
21 
117-3 
5-6 
June. 
5-3 
6 
5-8 
7 
5-5 
9 
50 
7 
21 
115-4 
5-5 
July. 
4-7 
6 
4-9 
6 
6-6 
7 
6-3 
5 
24 
134-9 
5-6 
August. 
5-8 
6 
5-2 
11 
6-5 
7 
7-5 
5 
29 
174-6 
6-0 
September. 
47 
16 
4-2 
9 
72 
7 
120 
2 
34 
197-6 
5-8 
October. 
41 
11 
61 
4 
5-4 
6 
60 
6 
26 
137-9 
5-3 
November. 
6-1 
6 
60 
5 
4-6 
1 
7'6 
6 
24 
153-0 
6-4 
December. 
5-8 
9 
5-1 
3 
7-9 
1 
0 
13 
75-3 
5-8 
Principally cloudy. 
January. 
3-8 
2 
4-6 
6 
2-6 
7 
15 
53-6 
3-6 
February. 
3-9 
2 
31 
6 
4-9 
3 
31 
6 
17 
59-7 
3-5 
March. 
3-2 
5 
1-6 
1 
10-5 
1 
4-2 
5 
12 
48-8 
4-1 
April. 
2-2 
6 
3-9 
1 
2-8 
1 
7-3 
2 
10 
34-6 
3-5 
May. 
21 
8 
50 
5 
5-8 
6 
60 
5 
20 
74-7 
3-7 
June. 
30 
5 
5-8 
1 
5-5 
9 
-13 
1 
25 
130-8 
5-2 
July. 
2-9 
11 
3-8 
3 
4-6 
6 
4-8 
9 
29 
113-5 
3-9 
August. 
3-6 
7 
3-6 
1 
70 
2 
7-9 
1 
11 
50-5 
4-6 
September. 
4-2 
2 
2-6 
4 
6-6 
3 
6-3 
5 
14 
70-7 
5-1 
October. 
2-8 
9 
4 6 
3 
4-6 
3 
6-3 
1 
16 
59-5 
3-7 
November. 
2-5 
9 
4-4 
2 
1-5 
2 
5-7 
3 
15 
51-6 
3-4 
December. 
3-7 
6 
8-0 
1 
5-7 
7 
0 
14 
70-3 
5-0 
Cloudy. 
January. 
2 3 
10 
3-4 
5 
0-7 
8 
20 
45-8 
2-0 
February. 
2 1 
19 
1-8 
5 
3-3 
11 
3-3 
7 
42 
109 0 
2-6 
March. 
0-6 
3 
1-9 
8 
5-3 
7 
1-8 
8 
26 
681 
2-6 
April. 
1-9 
4 
1-4 
5 
2-8 
4 
21 
3 
16 
32-3 
2-0 
Mav. 
0-4 
6 
1-9 
3 
2-6 
12 
41 
9 
30 
80-0 
2-7 
June. 
0-3 
6 
1-2 
2 
3-2 
6 
3-7 
2 
16 
27-8 
1-7 
July. 
0-8 
7 
3-7 
3 
3-8 
5 
31 
4 
19 
48-4 
2-6 
August. 
0-6 
8 
2-9 
3 
3-9 
2 
4-4 
7 
20 
54-0 
2-7 
September. 
2-8 
2 
20 
5 
5-1 
3 
5-4 
5 
15 
57-7 
3 8 
October. 
1-5 
5 
2-7 
7 
2-4 
6 
4-7 
10 
28 
88-4 
3-2 
November. 
2-4 
3 
4-0 
6 
20 
8 
2-9' 
11 
28 
791 
28 
December. 
4-3 
3 
2-8 
15 
3-3 
17 
3-4 
23 
56 
188-8 
3-3 
