LIEUT.-COLONEL SABINE ON TERRESTRIAL MAGNETISM. 
95 
gress from the lower into the higher inclinations, a = +'023, ^=+•984, c=+‘015 and 
d = ] : and for the remainder of the voyage tf=+’028, b, c and d, as before. 
In the Terror . — The place in which Mr. Fox’s apparatus was used in the Terror was 
about the same distance from the position of the standard compass, and in the same 
direction, as in the Erebus. A series of observations were made with it for the pur- 
pose of furnishing materials for the determination of the constants, at Hobarton in 
June 1841, and at the Falkland Islands in August 1842; and the inclination was 
also observed with the ship’s head on several points of the compass during the 
detention of the ships by the ice between the 6th and 16th of January 1842. In 
the case of the Erebus, we have found these latter observations of principal use in 
furnishing the values of the constants which apply to the greater part of the observa- 
tions of the voyage ; it may, therefore, be advisable to commence with the discussion 
of the corresponding series in the Terror. 
Inclinations observed on board Her Majesty’s ship Terror with needle F.C.B. used 
direct, during her detention by the ice from the 6th to the 16th of January 1842, be- 
tween the latitudes of — 65° 45' and —66° 20',and longitudes of 201° 46' and 204° 04'. 
Ship’s head 
by compass. 
Number of 
observations. 
Inclination 
observed. 
Ship’s head 
by compass. 
Number of 
observations. 
Inclination 
observed. | 
N. 
4 
— 8°1 19*5 
S. 
6 
— 7°8 30 
N. I E. 
2 
— 81 14 
s. f w. 
1 
— 78 21 
N. f E. 
1 
— 80 50 
s. by vv. 
1 
— 78 48 
N.N.E. 
3 
— 80 57 
s.w.byw.^w. 
1 
— 78 50 
N.E. 
2 
— 80 48 
s.w. by s. 
3 
-79 00 
n.e. by e. 
1 
— 80 26 
S.W. 
3 
-79 08 
E. I N. 
1 
-79 57 
s.w. \ w. 
1 
-79 08 
E. 
6 
-79 55 
s.w. by w. 
5 
— 79 21 
E. i S. 
1 
-79 45 
w.s.w. 
2 
-79 37 
e. by s. 
1 
-79 33 
w. by s. 
1 
— 80 05 
E.S.E. 
2 
-79 21 
w. 4 s. 
2 
-80 07 
s.E.by e.^ e. 
1 
-79 04 
N.W. 
2 
-81 09 
S.S.E. 
1 
— 78 42 
N. by w. 
1 
-81 15 
s. by e. 
4 
—78 37 
These observations manifest the general systematic character of the disturbance 
occasioned by the ship’s attraction ; they furnish indeed a remarkable example of the 
success with which the effect of the ship’s iron on the inclination may be investigated 
by observations made at sea. The disturbance appears to have not been strictly 
symmetrical, inasmuch as the inclinations observed on the western points somewhat 
exceed in amount those observed on the corresponding eastern points ; the same cir- 
cumstance took place in the observations at Hobarton ; but at the Falkland Islands, 
on the contrary, the inclinations observed on the eastern points were generally some- 
what the higher. A similar occasional departure from strict symmetry has before 
been noticed in the effect of the ship’s iron on the compass needle* ; in that case also 
* Philosophical Transactions, 1843, Part II. p. 152. 
MDCCCXLIV. 
O 
