Total Magnetic Force. 
253 
From this table, the principal minimum occurs about l h 10 m a.m. in the mean for the year, about midnight 
in winter, and about 2 h a.m. at the equinoxes and in summer. 
The results from Table XXVI. differ little from those deduced from|Table XXV. The secondary maxi- 
mum occurs earlier in summer than at the other periods, namely, about 6 h a.m. in summer, and about 8 h a.m. 
in winter and at the solstices. The following are the periods for the year : — 
The principal maximum occurs at 6 h p.m., Makerstoun mean time. 
The principal minimum occurs at l h 10 m a.m., 
A secondary maximum occurs at 8 h a.m., 
A secondary minimum occurs at 10 h 40 m a.m., 
Ranges of the Monthly Means op the Diurnal Variations of the Total Magnetic Force. 
It is evident, from the previous results, that the quantities in the last column of Table XXV. are not at 
all the diurnal ranges, as the minimum occurs near midnight. From Table XXVI., however, it appears that 
the range of the mean diurnal curve for the months about the winter solstice is 0-000240, about the equinoxes 
is 0-000744, and about the summer solstice is 0-000506 ; or, that the ranges are nearly in the following ratio : — 
Winter Solstice : Summer Solstice : Equinoxes = 1:2:3. 
TABLE XXVII. — Variations of the Total Force of the Earth's Magnetism with reference to the 
Moon's Age, Declination, and Distance from the Earth, as deduced from Tables IX. and XVI. 
Variations 
Variations 
After 
Variations 
After 
Variations 
Before 
Variations 
Before 
Variations 
Moon's 
of 
Moon's 
of 
Moon 
of 
Moon 
of 
and 
of 
and 
of 
Age. 
Magnetic 
Age. 
Magnetic 
farthest 
Magnetic 
farthest 
Magnetic 
After 
Magnetic 
After 
Magnetic 
Force. 
Force. 
North. 
Force. 
North. 
Force. 
Perigee. 
Force. 
Apogee. 
Force. 
Days. 
0-000 
Days. 
0-000 
Days. 
0-000 
Days. 
0-000 
Days. 
o-ooo 
Days. 
0-000 
15 
037 
0 
040 
0 
130 
14 
073 
7 
107 
7 
052 
16 
058 
1 
025 
1 
087 
15 
057 
6 
086 
6 
022 
17 
073 
2 
066 
2 
146 
16 
033 
5 
164 
5 
051 
18 
064 
3 
083 
3 
092 
17 
005 
4 
058 
4 
045 
19 
048 
4 
049 
4 
064 
18 
033 
3 
040 
3 
027 
20 
082 
5 
042 
5 
035 
19 
017 
2 
062 
2 
025 
21 
087 
6 
145 
6 
041 
20 
027 
1 
083 
1 
040 
22 
071 
7 
040 
7 
056 
21 
009 
P 
053 
A 
031 
23 
076 
8 
067 
8 
066 
22 
015 
1 
056 
1 
000 
24 
073 
9 
048 
9 
042 
23 
028 
2 
087 
2 
035 
25 
095 
10 
036 
10 
026 
24 
000 
3 
084 
3 
051 
26 
084 
11 
053 
11 
043 
25 
060 
4 
076 
4 
094 
27 
049 
12 
001 
12 
053 
26 
037 
5 
080 
5 
095 
28 
154 
13 
000 
13 
087 
27 
085 
6 
043 
6 
120 
29 
058 
14 
016 
7 
047 
7 
101 
Variations of the Total Magnetic Force with reference to the Moon's Age. 
Means of Groups. 
14 days to 16 days, Full Moon, 0-000037 
17 20 ••• 0-000067 
21 24 ••• 0-000077 
25 
28 
0-000095 
29 days to 
2 
6 
10 ... 
1 day, New Moon, 0 000041 
5 ••• 0-000060 
9 ••• 0-000075 
13 
0-000022 
From these means the total force is a minimum when the sun and moon are in opposition and in conjunction, 
and a maximum about the quadratures. The principal minimum occurs at the time of full moon. 
MAG. AND MET. OBS. 1843. 3 S 
