OF HEAT FROM THE MOON. 
599 
A comparison with Seidel’s Table* given below at once shows that the extinction 
of the moon’s radiant heat, although following a very similar law to that for stellar light, 
is not so great at considerable zenith-distances. 
At 79° zenith-distance the difference is about one tenth of the whole amount f. 
On the Connexion between the Moons Phase and the amount of her Radiant Heat. 
The observations were now reduced to the zenith, and the mean zenith-values deduced 
from each night, each observation having a weight apportioned to it inversely propor- 
tional to the number of which <pz is the logarithm. With the zenith-means and the 
extinction Table the values in column “ Gcalc.” of the following Table were calculated, 
and from the differences between observation and calculation the probable error of each 
observation and of the zenith-mean, z, was deduced by the usual formulae. These 
•are given in columns p.e. and^?.^. 
The probable errors are of course based on the assumption that no constant source of 
error existed ; we shall, however, see further on that most probably large constant errors 
were present on many occasions. 
* For the convenience of English readers we give Seidel’s Table for the estinction of light in the atmosphere 
(Fntersuchungen, p. 43) (for full title, see note, p. 505). 
For z < 14° the values of (j>z are imperceptible. 
0 . 
<pz. 
z . 
<pz. 
Z . 
<pz. 
z . 
<pz. 
z . 
<pz. 
o 
o 
0-006 
O 
o 
O 
13 
0-000 
28 
43 
0 023 
58 
0-083 
73 
0-233 
16 
19 
20 
21 
24 
o £ 
14 
o-ooi 
29 
0-007 
44 
0-026 
59 
0-090 
J 
7 
74 
0-249 
15 
o-ooi 
30 
0-007 
45 
0-028 
60 
0-097 
7 
75 
0-268 
16 
0 001 
31 
0-008 
46 
0-031 
61 
0-104 
7 
8 
9 
9 
10 
10 
10 
10 
10 
11 
13 
14 
15 
76 
0-288 
17 
0-001 
32 
0-009 
47 
0-034 
62 
0-112 
77 
0-309 
18 
0-002 
33 
0-010 
48 
0-038 
63 
0-121 
78 
0-333 
19 
0 003 
34 
0-011 
49 
0-041 
64 
0-130 
79 
0-359 
on 
20 
0-003 
35 
0-012 
50 
0-045 
65 
0-140 
80 
0-388 
40 
56 
21 
0-003 
36 
0-013 
51 
0 049 
66 
0-150 
81 
0-428 
OO 
0-003 
37 
0-014 
52 
0-053 
67 
0-160 
82 
0-484 
23 
24 
0-004 
0-004 
38 
39 
0-015 
0-016 
53 
54 
0-057 
0-062 
68 
69 
0-170 
0-180 
83 
84 
0-549 
0-616 
67 
68 
70 
25 
0-005 
40 
0-017 
55 
0-067 
70 
0-191 
85 
0-684 
26 
0-005 
41 
0-019 
56 
0-072 
71 
0-204 
86 
0-754 
27 
0-006 
42 
0-021 
57 
0-077 
72 
0-218 
28 
0-006 
43 
0-023 
58 
0-083 
73 
0-233 
At p. 503 of the £ Abhandlungen der Math.-phys. Classe der Iv. Akademie der AVissenschaften,’ Munich, 1861, 
Professor Seidel gives a new Table of <pz based on seventeen years’ observations ; but it differs so little (at most 
1 per cent.) from the Table here given, that Professor Seidel himself, for the sake of uniformity, continued to 
make use of the original Table only. AVhere the difference between the Tables for light and heat is greatest, 
Professor Seidel’s new Table lessens this difference by about one seventh part. 
t Note added Dec. 27, 1873. — Since writing the above, a possible way of accounting for the difference between 
the heat- and light-extinction curves has been found in the circumstance that the former was obtained from 
observations on the moon, the latter from observations on the stars. In the former case less loss would arise 
from bad definition at low altitudes than in the latter, as the greater part of the light and heat would be simply 
transferred from one part of the moon’s image to another ; whereas in the latter case it would be transferred 
from the star’s image to the sky round it, when it would only tend to lesson the contrast. Consequently it docs 
not necessarily follow that the foregoing observations point to different laws for light and heat. 
