DiUENAL VaEIATIONS FOK THE MAGNETIC DiP. Ixi 
into dip, reductions which have not been performed, the laws for the dip however are quite the same as those 
for the horizontal component, to which we refer. See also No. 141. 
Diurnal Variation of the Magnetic Dip. — The following Table is deduced from Tables 31 and 48. 
Table 57. — Diurnal Variations of Magnetic Dip for each Month, as deduced from the Regular Daily 
Observations made during the Four Years 1843 to 1846. 
Mak. 
Mean 
Time. 
Jan. 
I 
Feb. 
March. 
April. 
May. 
June. 
July. 
Aug. 
Sept. 
Oct. 
Nov. 
Dec. 
h. 
m. 
... 
12 
1 9 
0-658 
0-294 
0-214 
1-061 
1-743 
1-332 
1-509 
0 
0-755 
0-407 
0-466 
0-878 
13 
12 
0-724 
0-449 
0-773 
1-131 
1-782 
1-506 
1-670 
97S 
^ / o 
0-592 
0-352 
0-426 
0-744 
14 
12 
1-096 
0-578 
0-861 
1-767 
1-899 
1-647 
1-804 
1 
433 
0-930 
0-371 
0-462 
0-708 
15 
12 
0-452 
0-525 
0-478 
1-404 
1-989 
1-774 
1-914 
1 
470 
0-743 
0-070 
0-277 
0-588 
16 
12 
0-214 
0-409 
0-567 
1-303 
2-170 
1-918 
2- 129 
1 
550 
0-750 
0000 
0-156 
0-298 
17 
12 
0-000 
0-127 
0-538 
1-113 
2-200 
2-120 
2-320 
1 
908 
0-635 
0-157 
0-099 
0-104 
18 
12 
0-032 
0 040 
0-317 
1-282 
2-373 
2-515 
2-518 
2 
131 
0986 
0-440 
0-000 
0-000 
19 
12 
0-080 
0-030 
0-696 
1-631 
2-840 
2-883 
2-925 
2 
776 
1-756 
0-789 
0-234 
0-152 
20 
12 
0-366 
0-164 
1-344 
2-479 
3-455 
3-413 
3-485 
3 
548 
2-312 
1-557 
0-669 
0-373 
21 
12 
0-534 
0-610 
1-759 
3-133 
3-744 
3-706 
3-963 
3 
880 
2-884 
2-200 
1-273 
0-687 
22 
12 
0-836 
0-720 
2060 
3-264 
3-817 
3-655 
4-042 
3 
699 
2-924 
2-388 
1-457 
0-983 
23 
12 
0-767 
0-689 
1-824 
3-112 
3-353 
3-039 
3-459 
3 
040 
2-348 
2-092 
1-369 
1-008 
0 
12 
0-662 
0-473 
1-369 
2-430 
2-633 
2-230 
2-676 
2 
311 
1-610 
1-653 
0-937 
0-929 
1 
12 
0-302 
0-217 
0-693 
1-640 
1-762 
1-554 
2-022 
1 
371 
0-829 
0-920 
0-693 
0-713 
2 
12 
0-239 
0000 
0-336 
1-052 
1-260 
0-974 
1-197 
1 
041 
0-467 
0-710 
0-527 
0-558 
3 
12 
0-278 
0-009 
0-070 
0-632 
0-935 
0-689 
0-599 
0 
544 
0-210 
0-399 
0-496 
0-539 
4 
12 
0-227 
0-159 
0-000 
0-368 
0-189 
0-472 
0-372 
0 
409 
0-000 
0-445 
0-652 
0-477 
5 
12 
t 0-312 
0-242 
0-134 
0-007 
0-000 
0-191 
0-114 
0 
000 
0-133 
0-387 
0-208 
0-512 
6 
12 
0-444 
0-238 
0-292 
0-000 
0-107 
0-000 
0-000 
0 
126 
0-168 
0-274 
0-303 
0-283 
7 
12 
0-505 
0-129 
0135 
0-410 
0-138 
0-008 
0-296 
0 
206 
0-156 
0-339 
0-504 
0-493 
8 
12 
0-379 
0-128 
0-144 
0-601 
0-739 
0-372 
0-630 
0 
450 
0-491 
0-296 
0-440 
0-735 
9 
12 
0-439 
0-193 
0-221 
0-807 
1-251 
0-698 
1051 
0 
676 
0-399 
0-304 
0-608 
0-837 
10 
12 
0-514 
0-564 
0-249 
0-614 
1-447 
0-850 
1-303 
0 
675 
0-518 
0-331 
0-512 
0-857 
12 
0-493 
0-407 
0-034 
0-825 
1-693 
M84 
1-357 
0 
850 
0-446 
0-418 
0-566 
0-766 
128. The following are the approximate epochs of maxima and minima in apparent time as deduced from 
Table 57, distinguishing the epoch 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. 
h. m. 
h. m. 
h. m. 
h. m. 
h. m. 
h. m. 
h. m. 
h. m. 
h. m. 
h. m. 
Max. 
22 20 
+ 22 5 
+ 22 5 
+ 22 12 
22 5 
21 30 
21 45 
21 20 
+ 21 55 
+ 22 15 
+ 22 40 
+ 22 55 
Min. 
3 10 
- 2 30 
- 3 50 
- 5 45 
5 45 
6 40 
5 55 
5 25 
- 4 35 
8 15 
5 55 
5 55 
Max. 
+ 14 0 
12 45 
14 0 
14 30 
14 35 
12 25 
10 30 
11 15 
Min. 
-17 40 
-18 40 
17 50 
17 0 
17 5 
-16 25 
-18 15 
-18 15 
These epochs are very nearly the same as those obtained for the horizontal component No. 69. The 
diurnal variation of magnetic dip at Makers toun has only one maximum and minimum in the four months 
May to August, and it has two maxima and two minima in the remaining eight months. The morning 
minimum near 6*" .^.m., is the principal minimum in the four months October to January, in February the two 
minima are equal ; in the other months the principal or only minimum, occurs near &^ p.m. ; the principal 
maximum of dip occurs in each month with the exception of January near 10'^ a.m. It is only in the four 
winter months November to February that the 2*^ a.m. maximum is well marked. The variations of the epochs 
of maxima and minima will be found with most accuracy from Table 58, which contains the diurnal variations 
for groups of months. 
