LIEUT.-COLONEL SABINE ON TERRESTRIAL MAGNETISM. 
105 
Table of Index corrections for R. F. 5, face East, between —52° and —85°. 
Inclination. 
Correction. 
Inclination. 
Correction. 
O 
+ 3-2 
O 
✓ 
-52 
-69 
- 5-3 
-53 
+ 2*7 
-70 
— 5-8 
— 54 
+ 2*2 
-71 
— 6-3 
— 55 
+ 1-7 
-72 
- 6-8 
— 56 
+ 1-2 
-73 
- 7-3 
-57 
+ 0-7 
-74 
- 7-8 
— 58 
+ 0-2 
-75 
— 8-3 
-59 
— 0-3 
-76 
— 8-8 
-60 
-0-8 
-77 
- 9-3 
-61 
— 1-3 
-78 
- 9-8 
—62 
— 1-8 
-79 
— 10-3 
-63 
— 2-3 
— 80 
— 10-8 
-64 
— 2*8 
-81 
— 11-3 
—65 
-3-3 
-82 
-11-8 
-66 
-3-8 
-83 
— 12-3 
-67 
— 4*3 
— 84 
-12-8 
-68 
-4-8 
-85 
-13-3 
Index Correction of F. C. IS. for the Observations of Inclination in the Terror . — The 
observations of inclination at sea in this ship were all made with the face of the in- 
strument towards the east, and with the marked face of the needle towards the 
observer. We may examine the index corrections consequently in the same manner, 
and by comparison with the same complete determinations as in the case of the 
needle of the Erebus ; confining the comparison however to the land stations, be- 
cause F. C. B. was not observed with at either of the ice stations. 
The inclinations taken with this needle were observed both direct and with the aid 
of deflectors; the deflectors employed were a spare needle as “ deflector N” and 
“ deflector S” ; and the magnets of the apparatus, either used separately as “ magnet 
N,” or u magnet S,” or conjointly as “ magnets N S.” From some instrumental acci- 
dent, the inclinations observed with “ deflector N” were always considerably in defect 
of the others when the face of the circle was east ; with a corresponding excess with 
the face west, on the few occasions on shore when the observations were made in both 
positions. As the observations at sea were exclusively with the face east, it has been 
necessary on this account to consider separately those amongst them which were taken 
with “ deflector N,” and to obtain a distinct index correction for them. We will first 
examine the index corrections required for the direct observations, and for those with 
the other deflectors. 
The observations with F. C’. B. on shore at the four land stations, where the com- 
