17 
the intensity of magnetic forces , ^c. 
After these observations the magnets were wiped dry, and 
their poles of contrary names joined by bars of soft iron : to 
this circumstance I attribute the increase which, when next 
I used them, I found had taken place in their intensities. In 
the observations subsequent to these, I made use of two ther- 
mometers, one for each magnet, and observed the tempera- 
tures of both magnets at the beginning and at the conclusion 
of the observation. 
Table of the positions of the Points of Equilihrium corresponding to 
different Temperatures of the Magnets retaining a Magnetic Needle 
in Equilibro, 13 th of June. 
Time of 
commencing 
observation. 
Temperature of 
Points of Equilibrium. 
Temperature of 
Time of 
concluding 
observation. 
Mean Tempe- 
rature of the 
Magnets. 
C>vo 
On ^ 
N sc 
s E 
0 z 
CQ H 
E 
0 
JC 
00 
N. Mag. 
S. Mag. 
West. 
East. 
South. 
N. Mag. 
S. Mag. 
h. m. 
7 
7 35 
7 55 
B 26 
0 
63.0 
61 . 1 
71. 1 
66.2 
0 
62.6 
61.0 
71.1 
65.8 
0 / 
80 28 
81 12 
75 36 
77 40 
0 / 
80 28 
81 16 
75 44 
77 48 
d / 
0 18 E 
0 16 
0 18 
0 18 
0 
63.0 
61 .2 
71.0 
66.1 
0 
62.6 
61 .0 
71 .0 
65.7 
h. m. 
7 H 
7 40 
8 00 
8 32 
62.80 
61.08 
71.05 
65.95 
I have just mentioned that, on making these observations, 
I found the intensities of the magnets increased : on this 
account I was under the necessity of increasing their distances 
from the needle. The distances of their nearest ends from 
the centre of the needle were in this case 15.45 inches, or of 
their centres 21.41 inches : this value of R being substituted 
in the equation (C) gives 
M — F (.004553^04 + .0007880523 cos.>) = 0. (a^). 
As before, I calculate the following table from this equation. 
MDCCCXXV. 
D 
