Diurnal Variations for the Total Magnetic Force. 
Ixvii 
142. Diurnal Variation of the Total Magnetic Fo7-ce. — Table 62 has been computed from Tables 31 and 
48. The following are the approximate epochs of maxima and minima in apparent time, distinguishing those 
of the principal maximum by + , and of the principal minimum by — . 
Jan. Feb. March. April. May. June. July. Aug. Sept. Oct. Nov. Dec. 
h. m. h. m. b. m. h. m. h. in. h. m. h. m. h. m. h. m. h. m. h. m. h. m. 
Max. +5 35 + 5 0 + 5 5 + 5 55 + 5 45 + 6 30 + 5 35 + 5 35 + 4 55 + 3 40 + 6 25 + 6 20 
Min. -14 5 -14 0 -13 45 -13 0 -14 35 14 15 14 40 -14 5 -13 35 -16 15 -12 45 -14 45 
Max. 19 5 19 15 19 30 19 0 18 40 18 35 18 30 18 35 18 50 19 45 18 50 19 5 
Min. 22 0 21 55 22 30 22 45 -22 45 -23 0 -22 45 22 20 21 35 22 35 -22 50 -22 15 
The principal maximum of the total magnetic force occurs between 3^ 40™ and 6*^ 30™ p.m. in each 
month of the year ; it occurs latest in J une and November ; it occurs earliest in February and March, of the 
first six months, and in October and. September of the last six months of the year. The principal minimum 
occurs near 2^ a.m. in each month, with the exceptions of June and July, in which months it occurs near 11*^ 
A.M. ; in May, November, and December, the two minima are nearly equal. The secondary maximum occurs 
between 6^** and 7^^ a.m., and it is best marked in the months of March, April, and May, August, and Sep- 
tember. 
Table 63. — Diurnal Variations of the Total Magnetic Force for Different Periods, deduced from 
Table 62. 
Mak. 
Dec. 
Sept. 
Six Months. 
March. 
May. 
July. 
Aug. 
Sept. 
to 
Feb. 
March 
to 
Aug. 
Twelve 
Mean 
Time. 
Jan. 
Feb. 
April. 
June. 
Oct. 
Nov. 
Months. 
h. m. 
0-00 
000 
0-00 
0-00 
0-00 
0-09 
0-00 
o-on 
12 13 
; -0091 
-0236 
-0123 
-0154 
-0180 
-0135 
-0171 
-0154 
13 13 
-0094 
-0249 
-0168 
-0190 
-0192 
-0143 
-0202 
-0173 
14 13 
' -0135 
-0288 
-0180 
-0218 
-0198 
-0166 
-0229 
-0198 
15 13 
-0109 
-0207 
-0166 
-0197 
-0182 
-0145 
-0190 
-0168 
16 13 
! -0085 
-0180 
-0124 
-0158 
-0169 
-0127 
-0154 
-0141 
17 13 
-0064 
-0125 
-0089 
-0148 
-0132 
-0098 
-0121 
-0110 
18 13 
-0045 
-0067 
-0059 
-0117 
-0096 
-0070 
-0081 
-0076 
19 13 
-0037 
-0046 
-0065 
-0120 
-0075 
-0056 
-0077 
- 0067 
20 13 
-0041 
-0066 
-0116 
-0160 
-0085 
-0063 
-0114 
-0089 
21 13 
-0061 
-0111 
-0178 
-0202 
-0114 
-0087 
-0164 
-0126 
22 13 
-0075 
-0151 
-0230 
-0223 
-0124 
-0099 
-0201 
-0151 
23 13 
-0050 
-0148 
-0230 
-0219 
-0095 
-0072 
-0199 
-0136 
0 13 
-0021 
-0102 
-0163 
-0148 
-0001 
-0011 
-0138 
-0074 
1 13 
+ 0033 
0000 
-0060 
-0021 
+ 0098 
+ 0065 
-0027 
+ 0019 
2 13 
+ 0085 
+ 0130 
+ 0051 
+ 0106 
+ 0184 
+ 0134 
+ 0096 
+ 0115 
3 13 
+ 0133 
+ 0236 
+ 0167 
+ 0258 
+ 0285 
+ 0209 
+ 0220 
+ 0214 
4 13 
+ 0144 
+ 0305 
+ 0236 
+ 0361 
+ 0313 
+ 0228 
+ 0301 
+ 0264 
5 13 
+ 0152 
+ 0408 
+ 0358 
+ 0441 
+ 0313 
+ 0232 
+ 0402 
+ 0317 
6 13 
+ 0161 
+ 0399 
+ 0373 
+ 0441 
+ 0284 
+ 0222 
+ 0404 
+ 0313 
7 13 
+ 0142 
+ 0325 
+ 0356 
+ 0378 
+ 0209 
+ 0175 
+ 0353 
+ 0264 
8 13 
+ 0107 
+ 0210 
+ 0264 
+ 0265 
+ 0114 
+ 0110 
+ 0246 
+ 0178 
9 13 
+ 0056 
+ 0074 
+ 0141 
+ 0097 
+ 0020 
+ 0038 
+ 0104 
+ 0071 
10 13 
-0020 
- 0045 
+ 0048 
+ 0018 
-0055 
-0037 
+ 0007 
-0015 
11 13 
-0074 
-0074 
-0038 
-0096 
-0121 
-0097 
-0069 
-0084 
143. The means for groups of months having been obtained, as for the other magnetic elements, we find 
the approximate epochs for the mean diurnal variation in apparent time as follow : — 
Dec. Jan. Feb. March, April. May, June. July; Aug. Sept. Oct. Nov. 
Maximum, + 6^ 10™ p.m. + 5^ 25™ p.m. + 5^ 45™ p.m. + 5** 35™ p.m. + 4'' 50™ p.m. 
Minimum, -2^ 10™ a.m. - 2^ 10™ a.m. 1*^ 45™ a.m. - 2^ 10™ a.m. - 2^ 20™ a.m. 
Maximum, T'' 10™ a.m. 7^ 5™ a.m. 35™ a.m. G'' 35™ a.m. 35™ a.m. 
Minimum, G'' 55™ a.m. lO^^ 35™ a.m. -101»45™a.m. -10^ Sd'^ am. 10^ 20™ a.m. 
MAG. AND MET. OBS. 1845 AND 1846. r 
