Total Magnetic Force. 
251 
Variations of Magnetic Dip, with reference to the Moon's Distance from the Earth. 
Means of Groups. 
6 days after Apogee to 6 days before Perigee, 0'-119 
5 days to 2 days before Perigee, . . 0' - 297 
1 day before to 1 day after Perigee, . 0'-201 
2 days to 5 days after Perigee, . . 0'-163 
6 days after Perigee to 6 days before Apogee, 0'-197 
5 days to 2 days before Apogee, . . 0'-176 
1 day before to 1 day after Apogee, . 0'-125 
2 days to 5 days after Apogee, . . 0'-162 
Total Magnetic Force. 
The following results are deduced from the variations of the horizontal and vertical components by means 
of the formula 
A R aY „ n /a Y AX 
— cos 2 0 
/ A x A X\ 
R ~ 
where is the quantity in the following tables, and the quantities in the tables for the vertical and 
horizontal components respectively, and 6 the magnetic dip = 71° 18'. 
Secular Change of the Total Magnetic Force. 
From the mean secular changes for the two components of magnetic force, pages 235 and 245, we obtain 
Mean Secular Change of the Total Force, 1842 to 1843, = 0-001587. 
Annual Period of the Total Magnetic Force. 
From the quantities, pages 231 and 241, exhibiting the annual periods of the two components of magnetic 
force (the secular change being eliminated), the following quantities have been obtained, which shew the varia- 
tions of the total magnetic force for the different months of the year. 
Jan. Feb. March. April. May. June. July- Aug. Sept. Oct. Nov. Dec. 
0-000 I 406 358 127 000 036 257 248 227 058 156 313 395 
These quantities indicate maxima of the total force about the periods of the solstices, and minima about the 
periods of the equinoxes. One minimum occurs after the vernal euqinox, and the maximum at the winter solstice 
is greater than that at the summer solstice. 
TABLE XXV. — Diurnal Variations of the Total Force of the Earth's Magnetism, deduced from 
Tables XI. and XVIII. 
Period. 
18\ 
20 h . 
22 h . 
23 h . 
OK 
2 b . 
4 h . 
6K 
8K 
10K 
Range. 
0-000 
0-000 
0-000 
0-000 
0-000 
0-000 
•000 
0-000 
0000 
0-000 
0-000 
January 
000 
052 
032 
058 
114 
121 
150 
159 
144 
159 
February 
000 
078 
031 
025 
069 
152 
194 
219 
156 
219 
March 
063 
107 
063 
000 
071 
187 
304 
325 
206 
325 
April 
034 
076 
045 
000 
117 
340 
658 
494 
250 
658 
May 
151 
168 
085 
000 
119 
296 
434 
471 
182 
471 
June 
144 
171 
070 
000 
074 
247 
385 
411 
309 
411 
July 
057 
105 
041 
000 
155 
379 
450 
455 
271 
455 
August 
095 
136 
082 
000 
194 
339 
459 
417 
288 
459 
September 
000 
089 
048 
006 
150 
278 
284 
205 
081 
284 
