110 
LIEUT.-COLONEL SABINE ON TERRESTRIAL MAGNETISM. 
Besides the four land stations at which the intensities shown by the needles of the 
two ships have been thus compared, we have also one ice station in lat. —65° 47', 
long. 202° 08', at which similar comparisons may be instituted. The deflections and 
intensities were as follows : — 
Erebus. Terror. 
Deflection. 
Ther. 
Intensity. 
Deflection. 
Ther. 
Intensity. 
grs. 
O 1 
O 
grs. 
O / 
O 
r 2 
12 130 
50 
1-940 
r i 
11 25-4 
53 
1-940 
cn 
3 
18 32-4 
54 
1-921 
H 
17 08-3 
53 
1-957 
wJ 
<D 
4 
24 49-3 
54 
1-952 
02 
c3 
<D 
O 
2 
23 02-9 
53 
1-979 
O 
Ph 
5 
32 02-4 
54 
1-936 
oi 
29 16-2 
53 
1-955 
16 
39 31-4 
55 
1-946 
pH 
3 
36 17‘4 
53 
1-935 
1-939 
3i 
43 23*5 
53 
1-932 
^ 2 
1-950 
Collecting these several results in one view, we have as follows : — 
Erebus. 
Terror. 
Difference. 
Intensity at Hobarton 
. 1-82 
1-82 
(Erebus in defect.) 
Intensity at Sydney 
. 1-685 
1-699 
•014 or 8 parts in 1000 
Intensity at the Bay of Islands . . . 
. 1-594 
1-607 
*013 or 8 parts in 1000 
Intensity on ice, lat. — 65° 49', long. 202° 02' 1 -939 
1-950 
•01 lor 7 parts in 1000 
Intensity at Port Louis, Falkland Islands 
. 1*322 
1-336 
•0 1 4 or 1 0 parts in 1 000 
The difference between the results given by the needles of the two ships, though 
small, is so consistently shown at all the stations during the voyage, that we cannot 
hesitate to attribute it to the occurrence of a change of corresponding amount in the 
magnetism of one needle or the other, between the observations at Hobarton in April 
1841, and those at Sydney in July of the same year. If we further compare the 
intensities observed at sea by the two ships on the passage from Hobarton to Sydney, 
we find that a similar difference prevails in them ; and we are therefore led to the 
conclusion, either that the needle of the Terror gained, or that the needle of the 
Erebus lost, a very small portion of magnetism, in the period between the observa- 
tions at Hobarton in April 1841, and the departure of the Expedition from that port 
in the following July. Now experience has shown that a loss of magnetism is no 
unfrequent occurrence, whilst a gain is extremely rare, happening only, as far as we 
know, from such an accident as the contact of a needle with a more powerful magnet 
than itself. We may therefore conclude with great probability that the needle of the 
Erebus sustained a small loss of magnetism between April and J uly 1841 , antecedent to 
all the observations of the voyage, causing the intensities derived with it, when computed 
in reference to the angles of defection observed at Hobarton in April 1841, to require 
to be increased about one hundredth part, or more precisely 8 parts in 1000, in order 
