346 
MAGNETIC SURVEY OF A PART OF THE SOUTHERN HEMISPHERE. 
of Cape Horn and of the Cape of Good Hope, which will complete the survey of the 
high latitudes of the southern hemisphere. 
I propose then to combine in one general view the several portions of the southern 
survey which have been successively communicated ; and I shall reserve until that 
occasion, as more convenient than the present, such general remarks as suggest 
themselves in reference to the magnetic lines determined in the present Number. 
“ Report on the Magnetic Observations made in Her Majesty's hired bark Pagoda, 
from January to June 1845, by Lieut. Henry Clerk of the Royal Ar'tillery. 
“ 1 . Calculation of Corrections for the Ship's Local Attraction. 
“ To obtain the corrections for the observations of the Declination, the deviations 
of the compass were observed on each of the sixteen principal points at the Cape of 
Good Hope, King George’s Sound, the Mauritius, and again at the Cape on the 
return of the Expedition. The following are the observations : — 
Ship’s head. 
Cape of Good Hope. 
King George’s 
Mauritius. 
January. 
June. 
Sound. 
N. 
o / 
0 12 + 
6 20 + 
O / 
0 15 + 
6 20 + 
N.N.W. 
0 57 + 
Not observed. 
0 00 
0 30 + 
N.W. 
0 08- 
0 50 + 
0 20 + 
0 20- 
W.N.W. 
0 00 
0 50- 
1 40 — 
0 30 — 
w. 
0 13 — 
0 15 — 
1 40 — 
0 50 — 
w.s.w. 
0 28 — 
0 30- 
1 50 — 
1 10 — 
s.w. 
1 28 — 
1 20 — 
1 00 — 
1 10- 
s.s.w. 
1 06- 
1 25 — 
0 15 — 
0 50 — 
s. 
*1 48 + 
0 18 — 
0 50 + 
0 20 + 
S.S.E. 
0 42 + 
Not observed. 
0 55 + 
1 00 + 
S.E. 
1 12 + 
1 50 + 
2 20 + 
1 20 + 
E.S.E. 
1 27 + 
1 40 + 
3 10 + 
0 55 + 
E. 
0 57 + 
1 45 + 
2 40 + 
1 20 + 
E.N.E. 
0 27 + 
1 50 + 
3 10 + 
0 50 + 
N.E. 
0 12 + 
1 35 + 
3 30 + 
1 20 + 
N.N.E. 
0 32 + 
1 13 + 
2 35 + 
1 20 + 
The + sign denotes a deviation of the north end towards the west. 
“The values of & (the Inclination) being as follows, viz. — 
Cape of Good Hope . . . $=—53 44 
King George’s Sound . . . $= — 65 04 
Mauritius $= — 53 56 
“From these observations we can obtain the values of a and b by the formulae in 
No. V. of the Contributions to Terrestrial Magnetism -f-, which give the following 
values, viz. — 
* This observation is evidently erroneous. 
f Philosophical Transactions, 1843, Part II. p. 148 
