repetition of Mr. Christie's experiments , &c. 199 
IV. 
Table of the mean deviations due to the rotation of the plate, 
its plane being a tangent to the sphere, and its centre at 
the distance of 13 inches from the centre of the needle. 
Position of the 
plate’s centre. 
Zero, or mean read- 
ing of north end of 
needle before rota- 
tion. 
Mean of readings of 
north end of needle 
after plate had re- 
volved, its upper 
edge. 
Mean deviation of 
north end of needle 
due to rotation of 
plate, its upper edge 
Mean deviation due 
to rotation in oppo- 
site directions. 
Temperature. 
Fahrenheit, 
Remarks, 
From East 
to West. 
From West 
to East. 
From East 
to West. 
FromWest 
to East. 
I at. 
Long. 
O 
O 
O / 
0 / 
O / 
O / 
3 40W 
O / 
0 , 
O 
O 
90 
0 28 E 
3 12W 
4 2 E 
3 34 E 
+ 7 H 
+ 7 k 
3 turns, slow. 
O 
27O 
1 20 E 
3 4°W 
3 14E 
5 00W 
1 54 E 
— 6 54 
+ 94 
3 turns. 
s 4 s 
90 
28 52W 
27 52W 
3 32 E 
1 00 E 
32 24 E 
+ 3 1 24 
+ 34 
1 turn in 1 min. 
54 s 
27O 
1 05 E 
0 10W 
1 48 E 
1 15W 
0 43 E 
- 1 58 
+ 32 
1 turn in 1 min. 
90 s 
1 13W 
1 20W 
0 57W 
0 7 W 
0 16 E 
— 0 23 
+ 10 
3 turns. 
sH N 
90 
2 11 E 
1 8 E 
3 3 E 
1 3W 
0 52 E 
+ « 55 
+ 3 i| 
1 turn in 1 min. 
54 n 
270 
7 2W 
15 43W 
18 35 E 
8 41W 
25 37 E 
-34 18 
+ 32 
1 turn in 1 min. 
90N 
1 52 E 
1 40 E 
1 42 E 
0 12W 
0 10W 
+ 02 
+ 10 
3 turns. 
From Nor. 
From Sou h 
From Nor. 
From Sou* 1 
to South 
to North. 
to South. 
to North. 
0 
O 
1 8 E 
I 8 E 
i 8 E 
O OO 
O OO 
0 OO 
+ 9 i 
3 turns, slow. 
0 
180 
1 27 E 
1 33 E 
1 30 E 
O 6 E 
0 3 E 
— 03 
+ 10 
3 turns. 
s 
O 
42 4W 
41 42 W 
40 00W 
O 22 E 
2 4 E 
— 1 42 
+ 35 
1 turn in 1 min. 
54 s 
l8o 
45 35 E 
44 3 * E 
42 35 E 
I 4W 
3 00W 
— 1 56 
+ 32 
1 turn in 1 min. 
5 2 fN 
O 
44 36 E 
44 12 E 
42 19 E 
O 24W 
2 17W 
+ * 53 
+ 33 
1 turn in 1 min. 
54 N 
180 
43 8W 
41 53W 
40 21 W 
i 15 E 
2 47 E 
+ 1 32 
+ 3 6 
1 turn in 1 min. 
Some observations similar to these were made with the 
centre of the plate at the distance of 16 inches from that of 
the needle, in which the peculiar effects, already pointed out 
in this experiment, were exhibited with greater regularity, 
though to a less extent ; but as the whole series was not 
completed, they have been omitted here, and are deposited 
along with other observations on the effects produced on the 
needle by oscillating the plate in different arcs. 
HENRY FOSTER. 
Port Bowen, July i z, 1825. 
