198 Lieut. Foster’s account of the 
III. 
Table of the deviations due to rotation of the plate, its plane 
being in the plane of the equator, and its centre 15 inches 
from that of the needle. 
Position of the ) Lat. = o° 
centre of plate j Long.= o° 
Lat. ™ o° 
Long. =90° 
Lat. ~ o° 
Long. 1= 180 0 
Lat. ~ o° 
Long. = 270° 
Temperature. 
Fahrenheit. 
Remarks. 
Direction of rota- ] 
tion of upper >- 
edge of plate J 
From East 
to West. 
From West 
to East. 
From East 
to West. 
From West 
to East. 
From East 
to West. 
From West 
to East. 
From East 
to West. 
From West 
to East. 
Points on plate co- 
inciding with 
fixed mark 
CM N — 
0 + OON ft 
OOOOOO 
0 / 
12 15 E 
14 00 E 
1 7 20 E 
13 3 ° E 
11 40 E 
3 4°E 
O / 
12 OO E 
*3 45 E 
17 10 E 
13 20 E 
11 45 E 
3 4°E 
0 / 
4 O E 
6 10W 
4 3 oW 
3 00W 
0 30 E 
3 10 E 
O / 
4 20 E 
5 40W 
4 coW 
3 00W 
0 30 E 
3 10 E 
0 / 
6 20 E 
9 30 E 
17 00 E 
8 00 E 
6 20 E 
2 40 E 
O / 
6 00 E 
8 40 E 
16 40 E 
7 40 E 
6 00 E 
2 20 E 
0 / 
7 0 E 
3 30 E 
4 20 E 
1 40 E 
7 20 E 
5 55 E 
0 / 
7 00 E 
3 4°E 
4 20 E 
1 40 E 
7 20 E 
5 5° E 
O 
+ 18 
• • • • 
+ I8J 
1 3 gentle 
/ turns 
Means . 
12 4iE 
1 1 56I E 
2 oW 
1 20W 
8 i8±-E 
7 53 t E 
4 5 7 h E 
4 58^ E 
+ i8| 
Deviations due to t 
rotation in oppo- f 
site directions | 
+ °° 7 h' 
— oO 40' 
+ o° 25' 
- o° of' 
The amount of deviations caused by rotation in this adjust- 
ment of the plate to the compass, being so small and irre- 
gular, they may be considered as due to the circumstance of 
the plate not accurately occupying the place assigned to it, 
since the slight inequalities of the surface of the plate did 
not admit of the pivot of the needle being absolutely placed 
in its plane produced. 
The character + is prefixed to those deviations, the direc- 
tion of which, were towards that point, from whence the 
upper edge cf the plate was first turned, and — when the 
contrary. 
