INEQUALITIES OE TEEEESTEIAL MAGNETISM. 
421 
Lunar 
Hour. 
Luno-Diurnal Inequality in Horizontal Force. 
1858. 
1859. 
1860. 
1861. 
1862. 
1863. 
Mean, 
1858-1863. 
0 
-0-00004 
+ 0-00009 
+ 0*00002 
+ 0-00012 
+ 0-00003 
+ 0-00004 
+ 0-000043 
1 
— 
1 
+ 
10 
+ 
4 
+ 
6 
+ 
5 
— 
2 
+ 
38 
2 
0 
+ 
10 
+ 
13 
+ 
1 
+ 
3 
+ 
2 
+ 
48 
3 
+ 
4 
+ 
6 
+ 
14 
— 
1 
+ 
2 
+ 
4 
+ 
48 
4 
+ 
4 
+ 
6 
+ 
12 
— 
3 
+ 
2 
— 
3 
+ 
30 
5 
+ 
2 
+ 
3 
+ 
4 
— 
3 
— 
5 
— 
2 
— 
2 
6 
— 
6 
+ 
2 
0 
— 
7 
— 
17 
— 
5 
— 
55 
7 
— 
5 
— 
2 
+ 
1 
-r- 
13 
— 1 
11 
— 
4 
— 
57 
8 
— 
8 
— 
4 
+ 
1 
— 
11 
— 
13 
— 
2 
— 
62 
9 
— 
2 
— 
9 
+ 
6 
— 
4 
— 
11 
+ 
1 
— 
32 
10 
+ 
3 
— 
8 
0 
— 
5 
— 
16 
+ 
7 
— 
32 
11 
+ 
8 
— 
12 
+ 
7 
— 
3 
— 
1 
+ 
8 
+ 
12 
12 
+ 
14 
— 
6 
+ 
9 
— 
5 
+ 
2 
+ 
8 
+ 
37 
13 
+ 
8 
— 
5 
+ 
6 
- 
1 
+ 
12 
+ 
11 
+ 
52 
14 
+ 
7 
— 
5 
+ 
4 
+ 
5 
+ 
14 
+ 
11 
+ 
60 
15 
+ 
4 
— 
2 
0 
+ 
6 
+ 
14 
+ 
7 
+ 
48 
16 
+ 
3 
+ 
3 
— 
3 
— 
1 
+ 
13 
— 
l 
+ 
23 
17 
— 
1 
+ 
4 
— 
5 
+ 
3 
+ 
6 
— 
2 
+ 
8 
18 
— 
2 
+ 
1 
— 
13 
+ 
3 
+ 
2 
— 
6 
— 
25 
19 
— 
6 
— 
1 
— 
12 
+ 
5 
— 
5 
— 
4 
— 
38 
20 
— 
7 
— 
5 
— 
13 
+ 
6 
— 
1 
— 
8 
— 
47 
21 
— 
7 
— 
4 
— 
18 
— 
1 
— 
8 
— 
13 
— 
85 
22 
— 
7 
+ 
3 
— 
10 
+ 
7 
— 
4 
— 
11 
— 
37 
23 
- 
4 
+ 
5 
+ 
2 
+ 
9 
+ 
2 
0 
+ 
23 
The accordance, in general character, of the numbers in the last columns, derived from 
the observations 1858 to 1863, with those derived from the observations 1848 to 1857 
(Greenwich Magnetical and Meteorological Observations, 1859) is so striking, as to give 
great confidence in the mean of a few years’ observation, and to justify the breaking-up 
of the entire period 1848 to 1863 (of which the observations and reductions necessarily 
form one connected and uniform series) in any way that physical considerations may 
suggest. Now, remarking the singular difference for different years which has presented 
itself in the discussion of the solar inequalities, it appeared to me very desirable to 
examine whether there is any discoverable difference in the lunar inequalities for the 
same years. For this purpose, I divided the years into the following groups defined by 
the magnitude of the curves in the solar-diumal inequalities : — 
Large curves . . . 1848 to 1852 ; 
Small curves . . . 1853 to 1857 ; 
Small curves . . . 1858 and 1861 ; 
Large curves . . . 1859, 1860, 1862, 1863. 
The means for these periods were taken ; the first and fourth were united, forming a 
double mean for large curves, and the second and third were united, forming a double 
mean for small curves ; and in each system the numbers for the groups of three adjacent 
hours, 0 h to 2 h , 3 h to 5 h , &c., were added together. Thus were obtained the following : — 
