82 
SUPPLEMENT* 
pended horizontally the needle that was used only for the deter¬ 
mination of the intensity of the magnetic force, first by three 
or four delicate fibres of floss silk. It remained, however, exactly 
in the position in which it was placed. A single fibre of the 
floss silk was next tried, and lastly a single fibre of flax. All 
these failing to demonstrate the smallest amount of horizontal 
attraction, a second needle was treated in a similar manner, and 
in all these attempts I was equally unsuccessful. The top of 
the instrument being so constructed as to admit of a half-circle 
of torsion, this was next tried; but the needle was moved from 
its position in nearly the same amount as the arc described by 
the point of suspension, showing that the smallest amount of 
torsion was sufficient to overcome the directive energy of the 
needle. 
The needle was now removed to the dipping apparatus, and 
the following observations on the intensity of the vertical force 
of the needle were obtained, upon the supposition, that in 
whatever direction a given number of vibrations in the same 
arc were made in the shortest time, that might be assumed as 
the magnetic meridian The direction of the needle is given 
in true bearings. 
S. 50 c W. 
S. 80° W 
N. 70® W 
N. 40® V 
N. 10° W, 
N. 20 o W. 
and 
and 
and 
ana 
and 
and 
N. 50° E. 
N. 80° E. 
N. 70® E 
S. 40° E. 
S. 
10° E. 
S. 20° W. 
h m s 
h m s 
h m s 
h m s 
h 
m a 
h m s 
10 34 20 
10 37 287 
10 40 50‘2 
10 44 3 
10 
46 59 5 
10 49 47-5 
43 
52*5 
41 135 
26-5 
47 23 
50 10-5 
35 5‘2 
33 14'5 
36*5 
49‘2 
45-5 
33-2 
27 
36*2 
57‘5 
45 10*5 
48 7*5 
547 
48’5 
68 
42 19 
32-5 
29 
51 16*2 
36 10-2 
39 187 
407 
54 
507 
37‘5 
50 Vib"’ in 1 50*2 
1 50 
1 50-5 
1 51 
1 51-2 
1 50 
From these observations it was equally impossible to assign 
a direction to the magnetic meridian, the slight differences 
being within the limits of the errors of observation, and the 
amount of the inclination or dip of the needle in each of these 
directions being precisely the same. A diminution of force, 
however, may seem to obtain in the directions of S. 10° E. and 
