DiUENAL VaEIATIONS FOR THE HORIZONTAL COMPONENT. 
xxxix 
and from October to September, tlie morning maximum becomes smaller in comparison with the afternoon 
maximum ; and in May and August there are traces of the former which wholly disappear in June and July. 
The forenoon minimum occurs earliest in August, and before lO'^ a.m. in the four months from June till Sep- 
tember ; it occm-s latest in November and December, and after 10^ a.m. in the seven months October till 
April : the afternoon maximum occurs eai-liest for the first six months of the year, in February, and for the 
last six months, in September; it occurs latest in June and December. In order to destroy the smaller ir- 
regularities, means for gToiips of months have been taken ; the same groups have been used as those already 
adopted for the magnetic declination (No. 31). 
Table 32. — Diurnal Variations of the Horizontal Component of Magnetic Force for Different Periods, 
deduced from Table 31. 
Six Months. 
Mak. 
Mean 
Time. 
Dec. 
.J an. 
Feb. 
Sept. 
uct. 
Nov. 
March. 
April. 
May. 
June. 
July. 
Aug. 
Sept. 
to 
Feb. 
March 
to 
Aug. 
Twelve 
Months. 
h. m. 
0-00 
0-00 
0-00 
0-00 
o-on 
O'OO 
O'OD 
0-00 
12 12 
1 -0232 
+ 0062 
+ 0026 
+ 0212 
-0006 
-0119 
+ 0100 
-0010 
13 12 
-0260 
-0223 
- 01 10 
-0029 
+ 0056 
-0102 
- 0121 
-0112 
14 12 
-0435 
- 0574 
-0234 
-0182 
-0063 
-0249 
-0330 
-0290 
15 12 
-0174 
-0171 
- 0314 
-0225 
+ 0148 
-0013 
-0237 
-0125 
16 12 
+ 0035 
-0138 
-0412 
-0312 
+ 0213 
+ 0124 
-0287 
-0082 
17 12 
+ 0255 
+ 0010 
- 0477 
-0540 
+ 0254 
+ 0254 
-0336 
— 0040 
18 12 
! +0319 
+ 0091 
-0691 
-0690 
+ 0136 
+ 0227 
- 0430 
-0101 
19 12 
+ 0273 
-0201 
- 1058 
- 1146 
-0231 
+ 0021 
-0802 
-0390 
20 12 
+ 0084 
-0866 
- 1603 
- 1761 
-0747 
-0332 
- 1410 
-0871 
21 12 
-0203 
- 1373 
- 1916 
-2152 
- 1299 
-0751 
- 1814 
- 1 283 
22 12 
-0420 
- 1599 
- 1977 
-2129 
-1428 
-0924 
- 1902 
- 1413 
23 12 
-0374 
- 1429 
- 1511 
- 1589 
- 1122 
-0748 
- 1510 
- 1129 
0 12 
-0229 
-0892 
-0784 
-0866 
-0566 
-0398 
-0847 
-0623 
1 12 
+ 0064 
-0159 
-0014 
-0052 
+ 0039 
+ 0051 
-0075 
-0012 
2 12 
+ 0241 
+ 0379 
+ 0562 
+ 0573 
+ 0337 
+ 0289 
+ 0505 
+ 0397 
3 12 
+ 0281 
+ 0782 
+ 0942 
+ 1197 
+ 0610 
+ 0445 
+ 0974 
+ 0709 
4 12 
+ 0281 
+ 0995 
+ 1476 
+ 1456 
+ 0640 
+ 0460 
+ 1309 
+ 0884 
5 12 
+ 0231 
+ 1195 
+ 1751 
+ 1824 
+ 0746 
+ 0488 
+ 1590 
+ 1039 
6 12 
+ 0269 
+ 1121 
+ 1803 
+ 1819 
+ 0713 
+ 0491 
+ 1581 
+ 1036 
7 12 
+ 0203 
+ 0938 
+ 1769 
+ 1594 
+ 0565 
+ 0384 
+ 1434 
+ 0909 
8 12 
+ 0135 
+ 0737 
+ 1260 
+ 1231 
+ 0404 
+ 0269 
+ 1076 
+ 0673 
9 12 
+ 0019 
+ 0478 
+ 0776 
+ 0784 
+ 0286 
+ 0152 
+ 0679 
+ 0416 
10 12 
-0191 
+ 0430 
+ 0532 
+ 0597 
+ 0197 
+ 0003 
+ 0520 
+ 0261 
11 12 
-0168 
+ 0403 
+ 0197 
+ 0385 
+ 0110 
-0029 
+ 0328 
+ 0149 
70. The following are the approximate epochs of maxima and minima in apparent time from Table 32. 
(See also Plate II.) 
Dec. Jan. Feb. Slarch, April. May, June. July, Aug. Sept. Oct. Nov. 
Minimum, 10^ 20^ a.m. 10^ 10^ a.m. 10^ 0^ a.m. 9^ 35™ a.m. 10^ 0™ a.m. 
Maximum, 0" p.m. 6^ 15™ p.m. 6^ 20m p.^. 5h 45ni p.^. 5h 50ra p^^. 
Minimum, 2^ 0™ a.m. 2^ 0™ a.m 2^ O™ a.m. 
Maximum, 6^ lO™ a.m. 5^ 45™ a.m 5^ 30™ a.m. 
From these means of groups, the forenoon minimum occurs earliest in July and August, and latest iu 
December to February ; the afternoon maximum occurs earliest in December to February, and latest in May 
and June ; the morning maximum occurs earliest in September to November, and latest in the three months 
thereafter ; the after-midnight minimum appears to occur generally about 2^ a.m. 
The previous conclusions are obtained from the means of all the daily observations ; the following Table 
contains means for the same groups of months, deduced from the 10 days selected in each month of 1844 as 
free from intermittent disturbance, and the 10 days similarly selected for each month of 1845. See Table 
XXVIII., p. 362, 1844, and Table XXV., p. 14, of this volume. 
MAG. AND MET. OBS. 1845 AND 1846. 
k 
