318 
Mr. Christie’s theory of the 
compass opposite to the line of junction of the copper ring with 
the circular plate of bismuth. I thus obtained the deviations 
of the needle when the compass was opposite to the outer 
edge of the copper, and when it was opposite to the line of 
junction of the copper and bismuth, in eight different posi- 
tions of the compass, in each case ; the heated point being, in 
each position of the compass, in four different positions with 
respect to the centre of the needle. 
The observed deviations, corresponding to the different 
angular positions of the place of heat from the needle, the 
centre of the plate being the angular point, are contained in 
the following table, where this angle is measured from the 
needle, in the direction of the sun’s daily motion, round the 
whole circle. 
Table of the deviations of the needle when the plane of the plate was at right angles to the 
plane of the meridian, and the centre of the needle opposite to the outer edge of the copper. 
Angular distance of the 
place of heat from the 
centre of the compass. 
The centre of the needle being in the plane of the 
meridian passing the plate’s centre. 
The centre of the needle being in the horizontal 
plane passing through the plate’s centre. 
Above the plate’s 
centre, and 
Below the plate’s centre, and 
To the east of the plate’s 
centre, and 
To the west of the plate's 
centre, and 
l’S inch 
north of its 
surface. 
1’3 inch 
south of its 
surface. 
l - 3 inch north 
of its surface. 
1-3 inch south 
of its surface. 
1-3 inch 
north of its 
surface. 
l - 3 inch 
south of its 
surface. 
1'3 inch 
north of its 
surface. 
1'3 inch 
south of its 
surface. 
0 
O 
9 ° 
I 80 
270 
0 / 
29 30 w 
24. 30 E 
5 00 E 
3 00 E 
26 45 E 
24 45 w 
9 15 W 
5 00 W 
0 1 
29 OO E 
6 OO W 
7 45 W 
1 1 30 W 
0 / 
28 15 W 
5 OO E 
7 OO E 
1 1 00 E 
O / 
6 15 W 
35 3 ° E 
0 05 E 
34 3 ° w 
0 ' ^ 
10 00 E 
32 30 W 
0 30 W 
34 00 E 
O / 
7 15 E 
30 00 W 
2 30 W 
25 30 E 
O / 
1 1 30 W 
33 °o E 
5 00 E 
26 30 W 
Table of the corresponding deviations of the needle when its centre was opposite to the 
line of junction of the copper and bismuth. 
0 
90 
1 80 
270 
47 3 ° W 
10 45 E 
23 30 E 
164 30 E 
48 00 E 
5 ijW 
26 00 W 
167 30 w 
44 45 E 
6 00 W 
15 30 W 
f 135 00W 
\ 61 15 W 
31 i 3 W 
6 45 E 
1 1 30 E 
165 00 E ? * 
43 30 E j 
8 30 W 
14 45 E 
0 30 W 
51 30 W 
10 45 E 
13 15 W 
2 30 w 
44 45 E 
6 00 E 
14 20 W 
3 00 W 
45 3° E 
13 45 w 
18 20 E 
4 15 E 
52 00 W 
* The upper numbers indicate the directions of the needle when first observed, 
the lower ones those which it assumed almost immediately afterwards. These 
directions correspond to different positions of equilibrium noticed in a former 
paper; Phil. Trans. 1823. 
