horizontal needle when under the influence of magnets. 369 
force urging the north end of the needle deviated towards 
the east, without changing its intensity, the deviations of the 
westerly and easterly points of equilibrium would be both minus , 
and that of the southerly point plus. These agree precisely 
with the conclusions I had previously drawn. 
In order to point out the effects of increasing or diminishing 
the forces which the magnets exerted on the needle, com- 
pared with the terrestrial forces, or the effects that would 
take place if, without changing their direction at any par- 
ticular time, the terrestrial forces decreased or increased in 
intensity, from both the last positions of the axis of the mag- 
nets, namely, N o° 40' E and N o° 50' W, I brought the mag- 
nets nearer to the centre, keeping their axes still in the same 
line, and observed the corresponding changes in the points of 
equilibrium at every ~ inch by which they approached the 
centre of the needle. 
Table of the Points of Equilibrium corresponding to several distances 
of the Magnets from the centre of the Needle , the angle between 
the axis of the Magnets and the meridian remaining the same. 
1 1 May, 9 h A. M. to Noon ; compass No. I. 
Angle between the axis of the magnets and the meridian. 
N. o° 40' E. 
N. c 
>° 50' w. 
Distances. 
Points of Equilibrium. 
Distances. 
Points of Equilibrium. 
16.95 
16.85 
*6 . 75 
16.65 
*6 . 55 
i6 - 4 S 
16.35 
16 . 25 
16.15 
16.05 
1 5 * 95 
N. 33 36 W. 
37 16 
41 22 
46 24 
50 08 
54 52 
58 46 
63 18 
70 06 
78 48 
no point. 
0 ./ 
no point 
no point 
N. 17*20 E. 
30 26 
40 32 
46 16 
52 3 ° 
57 » 6 
65 34 
74 ° 6 
no point 
0 t 
no point 
no point 
S. 17 10 W. 
13 16 
10 38 
8 50 
8 12 
7 18 
6 34 
6 12 
5 5 ° 
16.95 
16.85 
16.75 
16.65 
16.5s 
16.45 
16.35 
16.25 
16. 15 
16.05 
1 5 • 95 
0 / 
no point 
no point 
N. 27 40 W. 
34 32 
42 18 
50 04 
54 38 
59 5 ° 
66 14 
74 00 
no point 
N. 3° 34 E. 
36 20 
39 0 
45 38 
49 22 
55 38 
59 0 
64 14 
72 26 
83 00 
no point. 
0 / 
no point 
no point 
S. 16 20 E. 
10 18 
8 40 
7 16 
6 28 
5 16 
5 10 
5 06 
4 18 
* The equilibrium at this point was not stable ; at the opposite point S 17 0 10' W 
the needle was very steady. 
MDCCCXXIII. 3 B 
