30 
Mr. Christie on the effects of temperature on 
their intensities had increased, owing, I consider, to the same 
circumstance as before, and I therefore increased their dis- 
tances from the needle ; but after making the first days ob- 
servations, and comparing them with those made in doors, I 
found it necessary slightly to diminish these distances, in 
order that, at the same temperature of the magnets, the si- 
tuations of the points of equilibrium might more nearly agree 
in the two cases. During the observations of the first day, 
the distance of the nearest ends of the magnets from the cen- 
tre of the needle were 15.62 inches : so that the value of R 
is here 21.58 inches, and the equation C becomes, 
M — F (.004441190 + .0007549085 cos.^(p) =0 (a^) 
The observations are contained in the following table. 
Table of the positions oj the Points of Equilibrium corresponding to differ ent 
Temperatures of the Magnets retaining a Magnetic Needle in Equilibrio. 
I 7 th and 18 th June. 
Time of 
commencing 
observation. 
Temperature of 
the Magnets. 
Points of Equilibrium. 
Temperature of 
the Magnets. 
Time of 
concluding 
observation. 
Mean Tempe- 
rature of the 
Magnets. 
Barom. 
Therm. 
attached. 
North. 
South. 
West. 
East. 
South. 
North. 
South. 
June 
h. 
m 
0 
0 
0 1 
79 S8 
0 / 
80 46 
0 
/ 
0 
0 
h. m. 
0 
17 
19 
27 
49.6 
48.8 
0 
42 E 
49.8 
49.0 
19 32 
49-30 
*9 
S 3 
60.25 
60.25 
7 S 24 
7 S 46 
0 
32 E 
60.25 
60.25 
19 56 
60.25 
20 
IS 
68.4 
68.6 
72 02 
72 40 
0 
24 E 
67.8 
68.2 
20 19 
68.25 
20 
36 
74*9 
75.0 
69 36 
70 08 
0 
24 E 
74.2 
74-3 
20 41 
74.60 
21 
02 
61 .8 
62.0 
74 12 
74 24 
0 
14E 
61.5 
61 .7 
21 06 
61.75 
21 
26 
74.0 
74.2 
70 06 
70 24 
0 
08 E 
73-4 
73-6 
21 30 
73-80 
30-29 
55-75 
18 
7 
36 
SS -7 
ss-s 
75 00 
75 06 
0 
00 
SS -7 
5 S -4 
7 40 
SS-S8 
8 
00 
66.2 
66.0 
70 58 
71 28 
0 
02 E 
66.0 
65.8 
8 04 
66.00 
8 
2S 
73-8 
73-8 
68 12 
68 52 
0 
02 E 
73-4 
73-4 
8 28 
73.60 
8 
SI 
56.8 
S 7-4 
74 38 
74 44 
0 
02 E 
56.4 
57.0 
8 56 
56.90 
30.20 
56.00 
From these I calculate the following table by means of the 
equation 
