LINES OF MAGNETIC DECLINATION IN THE ATLANTIC. 
181 
furnished by swinging a ship in harbour, even if repeated in more than one locality, 
must be insufficient to furnish corrections for the observations which may be made 
at sea in passages from port to port, if unaccompanied by experimental data furnished 
from time to time during the passages themselves. 
Seeing therefore the importance of the conclusions to which I have been led, I have 
thought it desirable to collect together in one point of view on the present occasion 
all the observations which were made in the Erebus for the purpose of examining the 
disturbance of the compass, during the three years in which she was employed in 
the Antarctic Expedition, and to enter on a somewhat detailed discussion of them. 
Table I. — Disturbance of the Compass in H.M.S. Erebus. 
+ Implies a disturbance of the North end of the needle towards the West ; 
— towards the East. 
Direction 
of 
ship’s head. 
Gillingham 
S eptember 
1839. 
Port Praya, 
November 
1839. 
St. Helena, 
February 
1840. 
Cape of 
Good Hope, 
April 
1840. 
Kerguelen 
Island, 
July 
1840. 
Hobarton, 
October 
1840. 
Hobarton, 
June 
1841. 
Falkland 
Islands, 
August 
1842. 
Cape of 
Good Hope, 
April 
1843. 
Direction 
of 
ship’s head. 
O 
/ 
O 
/ 
O 
16 
O 
O 
/ 
O 
/ 
O 
O 
/ 
N. by w. 
+ 1 
12 
+ 0 
27 
-0 
02 
+0 
-0 
27 
-0 
35 
— 1 
28 
-0 
04 
-0 
37 
N. by w. 
N.N.W. 
+ 2 
01 
-fo 
20 
-0 
27 
+ 0 
10 
— 1 
08 
-0 
29 
-2 
15 
-0 
34 
— 1 
04 
N.N.W. 
N.w. by N. 
+ 2 
10 
+ 0 
52 
-0 
34 
+ 0 
02 
-2 
07 
— 1 
43 
-2 
48 
-0 
51 
— 1 
15 
N.W. by N. 
N.W. 
-1-3 
03 
+ 1 
15 
-0 
40 
-0 
03 
— 2 
02 
— 1 
59 
-3 
09 
— 1 
02 
— 1 
42 
N.w. 
N.w. by w. 
+ 3 
28 
+ 1 
25 
— 1 
03 
-0 
15 
-2 
27 
-2 
47 
-3 
27 
— 1 
01 
-2 
01 
N.W by w. 
W.N.W. 
-f3 
51 
-hi 
05 
-0 
25 
-0 
33 
— 3 
12 
— 3 
07 
— 4 
04 
— 1 
49 
-2 
35 
W.N.W. 
w. by N. 
+ 4 
09 
+ 1 
15 
-0 
29 
-0 
51 
-3 
36 
-3 
37 
— 4 
47 
-2 
10 
-2 
54 
w. by N. 
w. 
-1-4 
19 
+1 
33 
-0 
32 
— 1 
09 
-3 
41 
-4 
03 
-5 
13 
-2 
16 
— 3 
09 
w. 
w. by s.' 
-1-4 
40 
+ 1 
49 
— 0 
12 
— 1 
14 
-3 
56 
— 4 
02 
— 5 
11 
-2 
21 
-3 
17 
w. by s. 
w.s.w. 
-b4 
03 
-f 1 
24 
-1-0 
09 
— 1 
05 
-4 
06 
-4 
16 
— 4 
55 
— 2 
21 
-3 
09 
w.s.w. 
s.w. by w. 
+ 3 
24 
+ 1 
34 
+ 0 
08 
—1 
06 
-3 
47 
— 4 
27 
-4 
33 
-2 
14 
-2 
52 
s.w. by w. 
s.w. 
+ 2 
45 
+ 0 
26 
+ 0 
04 
-0 
52 
-3 
23 
-3 
55 
-3 
54 
— 1 
58 
— 2 
27 
s.w. 
s.w. by s. 
+ 2 
08 
-1-0 
09 
+ 0 
14 
-0 
40 
— 2 
34 
-3 
24 
-3 
13 
-1 
43 
— 1 
52 
s.w. by s. 
s.s.w. 
+ 1 
34 
-0 
02 
-0 
01 
-0 
02 
— 1 
53 
— 2 
18 
— 2 
30 
— 1 
17 
— 1 
12 
s.s.w. 
s. by w. 
+ 0 
52 
-hO 
10 
— 0 
09 
+ 0 
16 
-0 
45 
— 1 
27 
-0 
34 
-0 
39 
-0 
07 
s. by w. 
s. 
+ 0 
28 
-0 
39 
-0 
29 
+ 0 
39 
+ 0 
22 
-0 
38 
-hO 
29 
0 
00 
4-0 
33 
s. 
s. by E. 
— 0 
19 
-0 
32 
-0 
24 
+ 1 
14 
+ 1 
10 
+ 0 
21 
+ 2 
18 
+ 0 
44 
+ 1 
07 
s. by E. 
S.S.E. 
-0 
48 
-0 
42 
-0 
30 
-hi 
26 
-h2 
05 
+ 0 
39 
+ 2 
52 
+ 1 
13 
+ 1 
45 
S.S.E. 
s.E. by s. 
— 1 
23 
-0 
25 
-0 
25 
+1 
41 
+ 2 
50 
+ 1 
24 
-h3 
37 
+ 1 
41 
+ 2 
08 
S.E. by s. 
S.E. 
—1 
53 
— 1 
09 
-0 
21 
+ 2 
53 
+ 3 
21 
+ 1 
56 
4-4 
20 
+ 1 
55 
+ 2 
31 
s.E. 
s.E. by E. 
-2 
21 
— 1 
25 
— 0 
21 
+ 2 
01 
+ 3 
51 
+1 
46 
-h4 
46 
+ ^ 
07 
+ 2 
51 
S.E. by E. 
E.S.E. 
~2 
50 
— 1 
18 
-0 
06 
-hi 
43 
-h4 
12 
-h3 
29 
-h5 
31 
+ 2 
19 
+ 3 
15 
E.S.E. 
E. by s. 
— 3 
17 
-1 
44 
+ 0 
13 
+ 1 
34 
+ 3 
53 
-h3 
23 
-h5 
06 
+ 2 
16 
+ 3 
10 
E. by s. 
E. 
-3 
42 
— 1 
56 
+ 0 
32 
+ 1 
15 
-h3 
48 
+ 3 
50 
-h4 
53 
4-2 
07 
+ 2 
46 
E. 
E. by N. 
— 4 
53 
—2 
40 
+ 0 
55 
-hi 
02 
+ 3 
31 
+ 4 
06 
-h4 
32 
+ 1 
54 
+ 2 
30 
E. bv N. 
E.N.E. 
— 3 
46 
-2 
47 
+ 0 
57 
-hi 
51 
+ 3 
02 
+ 3 
41 
-h3 
52 
4-1 
44 
+ 2 
15 
E.N.E. 
N.E. by E. 
— 3 
18 
— 2 
30 
+ 0 
48 
-hO 
31 
+ 2 
13 
-h3 
33 
-h3 
31 
+ 1 
16 
+ 1 
59 
N.E. by E. 
N.E. 
— 2 
59 
— 2 
10 
-hi 
11 
+ 0 
22 
+ 2 
10 
-h3 
23 
+ 2 
54 
+ 0 
51 
4-1 
33 
N.E. 
N.E. by N. 
-2 
16 
— 2 
12 
-hO 
52 
-hO 
11 
+ 1 
32 
+ 3 
01 
-h2 
25 
+ 0 
41 
+ 1 
15 
N.E. by N. 
N.N.E. 
— 1 
39 
-1 
53 
-f 0 
28 
+ 0 
01 
+ 1 
01 
+ 2 
37 
-hi 
15 
+ 0 
41 
+ 0 
43 
N.N.E. 
N. by E. 
— 0 
49 
— 1 
17 
+ 0 
17 
+0 
24 
+ 0 
23 
h2 
17 
+ 0 
23 
+ 0 
28 
+ 0 
15 
N. by E. 
N. 
+ 0 
06 
-0 
56 
+ 0 
05 
+ 0 
24 
-0 
08 
-hi 
12 
+ 0 
41 
+ 0 
13 
-0 
20 
N. 
From the observations in September 1839, at Gillingham in the River Thames 
(where the ship had been stationary for many months), a table was formed by the 
well-known formulse derived from Poisson’s fundamental equations applicable to in- 
MDCCCXLIX. 2 B 
