LIEUT. CLERK’S REPORT: ELEMENTS OF REDUCTION. 
363 
“The value of I at the Cape has therefore been assumed provisionally as unity; 
subject to future correction should any appear to be required. 
“The spare needle 2 was always used as a deflector; the two small magnets were 
used conjointly only with this apparatus. 
“ Tables of equivalent weights were made at the Cape both before and after the 
Expedition, according to the method given in the instructions for the use of Mr. 
Fox’s instrument. The following Table contains the mean of the two series. 
Def. N. 
Def. S. 
Mag. N and S. 
Def. N. 
(Continued.) 
Def. S. 
(Continued.) 
Mag. N. and S. 
(Continued.) 
v '. 
v/. 
v\ 
u/. 
v\ 
w'. 
v'. 
w'. 
v f . 
vf. 
v'. 
«/. 
g r - „ 
o 
gr- 
o 
grs. 
o 
gr- 
o 
gr- 
grs. 
21 
1-816 
22 
1-950 
41 
3-608 
31 
1-843 
32 
1-935 
51 
2-786 
22 
1-835 
23 
1-964 
42 
3-522 
32 
1-828 
33 
1-918 
52 
2-717 
23 
1-850 
24 
1-972 
43 
3-438 
33 
1-814 
34 
1-903 
53 
2-654 
24 
1-861 
25 
1-977 
44 
3-350 
34 
1-801 
35 
1-891 
54 
2-595 
25 
1-867 
26 
1-983 
45 
3-262 
35 
1-788 
36 
1-868 
55 
2-535 
26 
1-868 
27 
1-980 
46 
3-179 
36 
1-770 
37 
1-852 
56 
2-480 
27 
1-867 
28 
1-977 
47 
3-093 
37 
1-756 
38 
1-833 
57 
2-428 
28 
1-866 
29 
1-968 
48 
3-013 
38 
1-744 
39 
1-812 
58 
2-377 
29 
1-861 
30 
1-960 
49 
2-933 
39 
1-726 
40 
1-793 
59 
2-330 
30 
1-858 
31 
1-946 
50 
2-853 
40 
1-707 
41 
1-775 
60 
2-278 
“With these values of w', and the following values of v and w, the values of I' have 
been calculated by the formula 
I'=I sm V ', W - when deflectors are used, and 
sin v'.w ’ 
T=I when weights are used. 
Values of v at the Cape of Good Hope. 
Date. 
Def. N. 
io=l-721. 
Def. S. 
10=1-782. 
Mag. N and S. 
io = 2-337. 
Weight 
1 grain. 
Weight 
2 grains. 
Weight 
2 grains. 
1844. 
o / 
o / 
O / 
Dec. 1. 
39 06 
40 38 
59 23 
21 30 
46 54 
65 22 
5. 
1845. 
39 01 
40 37 
59 22 
21 34 
46 33 
65 20 
June 30. 
39 31 
: 40 39 
58 16 
21 38 
46 32 
65 30 
July 2. 
39 22 
40 39 
58 21 
22 06 
46 21 
65 30 
Mean... 
39 15 
40 38 
58 51 
21 42 
46 35 
65 25 
“ From this Table it is evident that, with the exception of magnets N and S, the 
needles preserved their magnetism throughout the voyage. Magnets N and S lost 
magnetism to the amount of *033. The mean of the four observations have been 
taken; the early intensities by this method will therefore be rather too small, the 
latter ones rather too great. 
