LINES OF MAGNETIC DECLINATION IN THE ATLANTIC. 189 
declination (i. e. the coefficient A=0), the disturbance on the several points are as 
follows, viz. — 
Table II. — Disturbance of the Compass in H.M.S. Terror. 
Disturbances towards the west. 
Disturbances towards the west. 
Ship’s head. 
Falkland 
Islands, 
Aug. 17, 1842. 
Cape of 
Good Hope, 
April 20, 1843. 
Ship’s head. 
Falkland 
Islands, 
Aug. 17, 1842. 
Cape of 
Good Hope, 
April 20, 1843. 
N. 
+ 0 18 
-6 58 
s. 
-6 16 
+ 6 44 
N. by w. 
-0 02 
— 1 3 
s. by E. 
-0 08 
+ 1 56 
N.N.W. 
-0 17 
-1 6 
S.S.E. 
0 00 
+ 3 1 
K.w. by N. 
-0 48 
— 1 22 
s.E. by s. 
+ 0 47 
+ 3 2 
N.W. 
-1 19 
-2 20 
S.E. 
+ 1 .35 
+ 3 5 
N.w. by \T. 
-1 49 
— 2 12 
S.E. by E. 
+ 2 17 
+ 3 3 
W.N.W. 
-1 47 
-3 14 
E.S.E. 
+ 3 04 
+ 3 4 
w. by N. 
-2 07 
-3 35 
E. by s. 
+ 2 33 
+ 3 22 
w. 
— 2 30 
— 3 36 
E. 
+ 2 46 
+ 2 35 
w. by s. 
—2 21 
—3 8 
E. by N. 
-f2 27 
+ 2 27 
w.s.w. 
—2 12 
-2 35 
E.N.E. 
+ 1 58 
+ 1 53 
s.w. by w. 
— 2 21 
-2 1 
N.E. by E. 
+ 1 39 
+ 1 23 
s.w. 
— 1 33 
-1 33 
N.E. 
+ 1 13 
+ 1 8 
s.w. by s. 
— 1 05 
— 1 26 
N.E. by N. 
+ 1 11 
+ 1 I 
s.s.w. 
-0 47 
— 1 22 
N.N.E. 
-fO 34 
+ 0 30 
s. by w. 
-0 45 
-0 9 
N. by E. 
+ 0 27 
-0 27 
From these we have D=-}-l7^ and E=+6'; also at the Falk- 
land Islands, and —-054 at the Cape. For the reasons assigned in the case of the 
Erebus, I have taken — ’040 as applicable until the Terror sailed to the higher lati- 
tudes in December 1842, and have then increased it uniformly and progressively with 
the time until the first week in January 1843, when the south dip was greatest; and 
from this date until the arrival at the Cape I have employed —•054 (observed at the 
Cape), which was the greatest observed value of this term. 
The compass employed in this portion of the Terror’s voyage was made by Cum- 
mins, and had two cards, a light and a heavy one, the latter being- used exclusively in 
very bad weather. In a memorandum which I received from Captain Crozier, it is 
stated that the index errors were examined at the observatory in the Falkland Islands 
on the 23rd of August 1842, and found to require corrections, with the light card of 
+ 1° 13', and with the heavy card of —0° 40'. The cause of these errors does not 
appear to have been examined either during the voyage or after the return to England. 
The error of the light card, which was the one generally used, is in the opposite direc- 
tion to the error assigned to the compass of the Erebus examined at the same time ; 
and it is remarkable that throughout this portion of the voyage in which the two 
ships were always in company, the declinations observed in the Erebus are generally 
still more easterly than those of the Terror after the corrections for the compass 
error are applied, and that this disagreement would be greater if the corrections were 
not so applied. I have therefore felt the less hesitation in admitting and employing 
compass errors of such magnitude, the cause of which does not appear to have un- 
dergone investigation ; but 1 cannot avoid expressing the hope that as the state of 
2 c 
MDCCCXLIX. 
