VERTICAL COMPONENT OF MAGNETIC Forcr. 241 
tember till December. The diminution from January till December is 0:001731; if we refer to the previous 
attempt to connect the different series of observations, we find the mean annual diminution from the beginning 
of March 1848 till the beginning of March 1844 =213 micrometer divisions ; this, together with the rate of 
this change, will give 210 micrometer divisions (= 0-001890) for the diminution from January 1848 to January 
1844. If proportional parts of this be applied to the monthly means above, the secular change will be elimi- 
nated, and the annual period rendered more distinct. The corrected means are as follow :— 
Jan. Feb. March. April. May. June. July. Aug. Sept. Oct. Nov. Dec. 
0:01 | 6924 6899 6690 6555 6539 6771 6798 6793 6599 6716 6852 6925 
This indicates a maximum at mid-winter and at mid-summer, a minimum about April and a minimum in 
September. It seems, therefore, very probable that the same law holds for the vertical component as has al- 
ready been shewn to exist for the horizontal component, namely, mawima at the solstices, and minima at the 
uinones. 
: From the above the minima at the equinoxes seem to differ little, but the maximum at the winter solstice 
is considerably greater than that at the summer solstice. 
The range of the annual period is 0-000386. 
TABLE XVI.—Mean Variations of the Vertical Component of Magnetic Force, after eliminating the 
Secular Change, with reference to the Moon’s Age, Declination, and Distance from the Earth, 
for 1848. 
Variations Variations} After | Variations} After |Variations|/ Before | Variations} Before | Variations 
Moon’s} of Ver- | Moon | of Verti- of Verti- of Verti- and | of Verti- 
Age. | tical Com- . farthest | cal Com- cal Com- cal Com- | after | cal Com- 
ponent. . | North. | ponent. . | ponent. ponent, | Apogee. ponent. 
0-000 
118 
108 
0-000 f 0-000 
136 077 
094. 063 
151 
096 
091 
060 
062 
069 
067 
047 
040 
031 
055 
0-000 
078 
054 
067 
067 
041 
043 
053 
055 
000 
046 
064 
114 
114 
129 
110 
0-000 : | D 
055 
056 
081 
057 
048 
077 
076 
058 
Fy 
0 
Ss 
SI 
OnNDIAMPwWNHRr Os 
NOUR WHORE DEN wWhaADAT 
NOuRWNE PEN WRADN 
Table XVI. was formed from Table XV. in the manner already indicated, Table II. for the declination. 
VARIATIONS OF THE VERTICAL COMPONENT OF MAGNETIC FORCE WITH REFERENCE TO THE RELATIVE 
PosiTIoNns oF THE Sun, Moon, AND EARTH, AS INDICATED BY THE Moon’s AGE. 
The means shew, with considerable irregularities, mavima near the quadratures, and minima near the 
syzigies. The principal minimum occurs at the period of full moon, the following means of groups give the 
same result :— 
14 days to 16 days, Full Moon, 0-000041 29 days to 1 day, New Moon, 0:000031 
Ue eee 20 oer. 0-000066 Ddeiractts GyeOn 0:000046 
’ 25 ee 24... 0-000067 Glee eect anes 0:000079 
DOr. sear PAY ce 0:000083 LOR ese Ie essa 0:00003 - 
MAG. AND MET. oBs. 1843. 3P 
