364 
MAGNETIC SURVEY OF A PART OF THE SOUTHERN HEMISPHERE. 
“ The formulae for calculation are as follows 
Def. N 
Def. S 
Mag-. N and S . . 
Weight 1 grain 
Weight 2 grains . 
Weight 2^ grains 
I' = -3677 cosec v' . w'. 
I' = -3654 cosec v' . w'. 
I'=-3659 cosec v' . id. 
r='3698 cosec d . w'. 
T = - 7264 cosec d . id . 
I'=-9094 cosec d . id. 
“ Fox C. 9. — The values of the intensity at the Cape by the observations before and 
after the Expedition, by Fox, No. 1, are : — 
Before 1 = 0-999 1 _ 
. „ r > diff. -002. 
After 1=1-001 J 
“ These values agreeing so closely, we may assume that the intensity at King George’s 
Sound with this apparatus will be very near the truth, and that King George’s Sound 
may therefore be taken as a base station for needle A of C. 9, which was not observed 
at the Cape before our departure. The intensities were observed with needle A 
mounted, from the Cape to King George’s Sound, when the needle got unfortunately 
damaged, and it was necessary to replace it with needle B : one day’s observations 
had however been made before the accident, and these observations serve for calcu- 
lating the intensities taken on the voyage, assuming the intensity at King George’s 
Sound to be that given by the other apparatus, viz. 1-688. 
“The same deflectors and weights were used throughout ; the spare needle C as a 
deflector, the two small magnets both conjointly and separately. 
“Tables of equivalent weights for these deflectors, with needle A mounted, were 
obtained in the same way as in the case of the other apparatus. They are as follows : 
Def. N. 
Def. S. 
Mag. N and S. 
Mag. N. 
Mag. S. 1 
v'. 
V 
v'. 
w'. 1 
v\ 
w'. 
v'. 
w'. 
w'. | 
grs. 
grs. 
grs. 
o 
grs. 
o 
grs. 
50 
2-175 
50 
2-206 
70 
2-625 
50 
1-578 
50 
1-975 | 
49 
2 200 
49 
2 247 
69 
2-675 
49 
2-028 
49 
2-025 
48 
2-225 
48 
2-288 
68 
2-725 
48 
2-078 
48 
2-075 
47 
2-263 
47 
2-323 
67 
2-775 
47 
2-130 
47 
2-125 
46 
2-300 
46 
2-357 
66 
2-825 
46 
2-182 
46 
2-175 
45 
2-338 
45 
2-388 
65 
2-875 
45 
2-235 
45 
2-240 
44 
2-375 
44 
2-419 
64 
2-925 
44 
2-288 
44 
2-304 
43 
2*413 
43 
2-460 
63 
2-982 
43 
2-341 
43 
2-368 
42 
2-450 
42 
2-500 
62 
3-038 
42 
2-394 
42 
2-433 
41 
2-488 
41 
2-538 
61 
3-094 
41 
2-447 
41 
2-498 
40 
2-525 
40 
2-575 
60 
3-150 
40 
2-500 
40 
2-563 
39 
2-565 
39 
2615 
59 
3-222 
39 
2-570 
39 
2-623 
38 
2-605 
38 
2-655 
58 
3-294 
38 
2-640 
38 
2-683 
37 
2-645 
37 
2-695 
57 
3-365 
37 
2-710 
37 
2-743 
36 
2-685 
36 
2-735 
56 
3-436 
36 
2-780 
36 , 
2-803 
35 
2-725 
35 
2-775 
55 
3-507 
35 
2-850 
35 
2-863 
34 
2-755 
34 
2-806 
54 
3-595 
34 
2-900 
34 
2-937 
33 
2-785 
33 
2-837 
53 
3-683 
33 
2-950 
33 
3-011 
32 
2-815 
32 
2-869 
52 
3-770 
32 
3-000 
32 
3-085 
31 
2-845 
31 
2-901 
51 
3-857 
31 
3-050 
31 
3-158 
30 
2-875 
30 
2-932 
50 
3-944 
30 
3-100 
30 
3-232 
29 
2-900 
29 
2-954 
49 
4-047 
28 
2-925 
28 
2-975 
48 
4-150 
