416 
Mr. Christie on the effects of temperature on 
2nd. The same iron plate to the east of the compass. 
Angular distance 
of the plate’s 
centre from the 
equator. 
Angular velocity 
of the plate, and 
points opposite 
to the needle 
when plate sta- 
tionary. 
~c 
c 
n 
•M 
Ui 
O 
G 
4^ 1—1 
33 "S 
« 3 
CD O 
^ .5 
j 
20 
V 
a, c2 , 
<u ■< 
X! 
d X 
^ d 
o 
CD 
a 
C .u 
G ^ 
O 
<u 
U( 
G 
CD 
0 ) 
Slow 
^ 8 rev. 
i Slow 
^8 rev. 
i Slow 
50 i 
(,8 rev. 
^ Slow 
70 I 
8 rev. 
f Slow 
90 < 
1 8 rev. 
f Slow 
^ 8 rev. 
f Slow 
^ 8 rev. 
f Slow 
1 10 
130 
140 
160 
I o 
( 180 
per sec 
( 180 
per sec 
\ 180 
rev. per sec 
^ o 
^ i8o 
per sec 
) 180 
per sec 
\ 180 
per sec 
V o 
'^180 
per sec 
] o 
^ 180 
Direction of the N. end of the needle when plate sta- 
tionary after slow rotation, and also while the plate 
was rapidly revolving. 
\ 8 rev. per 
S Slow / 
I ^ 
o 
180 
8 rev. 
Plate’s centre in N. lat. 
Plate’s centre in S. lat. 
Upper edge of the plate revolving. 
N to S 
S to N 
N to S 
S to N 
0 / 
0 / 
0 / 
0 / 
9 55 E 
I 2 SW 
8 soW 
5 20 E 
5 00 E 
7 2 sW 
i6 30 
4 45W 
U 05 
4 2sW 
16 35 
I 35 E 
35 *5 
29 25 E 
39 40 
33 30W 
31 55 
26 25 
42 20 
37 30 
34 50 
27 2S 
42 25 
34 55 
42 30 
40 os 
53 45 
so so 
39 50 
37 30 
54 2S 
52 15 
42 10 
38 50 
S 3 20 
49 10 
48 55 
47 50 
59 ^5 
56 20 
45 30 
43 55 
59 30 
57 *5 
• 48 3 S 
45 45 
58 50 
55 40 
59 45 
57 55 
66 35 
64 40 
56 00 
54 30 
66 so 
6s 00 
58 25 
55 40 
66 25 
63 35 
71 00 
69 30 
75 10 
73 40 
67 10 
65 50 
75 10 
73 55 
. 70 40 
68 30 
74 20 
72 10 
83 25 
83 30 
81 10 
80 45 
80 20 
80 15 
83 00 
83 00 
82 20 
81 45 
81 15 
80 IS 
86 35 
87 30 
81 30 
82 20 
83 00 
84 25 
84 50 
8s 20 
. 8s so 
86 40 
82 20 
82 40 
77 00 
8s 20 
68 00 
77 20 
47 30 
73 15 
72 35 
81 IS 
. 51 40 
81 40 
67 10 
79 40 
Deviation due to the rota- 
tion of the plate’s upper 
edge from N to S, when 
plate’s centre was 
in N. lat. 
in S. lat. 
-) ” ' 
0 / 
1 5 56E 
6 29W 
7 45 E 
0 05W 
j 2 so 
2 45 
3 43 
3 45 
1 I 09 
I 16 
I 40 
■J 
2 os 
j. 0 40 
I 18 
I 2 S 
* 35 
1 0 50 
0 57 
1 23 
I 2 S 
[ 0 43 
0 41 
I os 
I 05 
1 0 00 
0 06 
0 18 
0 30 
I 0 3sW 
0 20 E 
0 10 E 
1 8 31W 
4 30 
IS 00 
6 IS 
From the inspection of these tables, it appears that the 
forces which are exerted on the needle during the rapid rota- 
tion of the plate, are always in the same direction as the 
forces which are derived from the slowest rotation, and which 
.continue to act after the rotation has ceased ; but that the 
