XXX 
Introduction to the Makerstoun Observations, 1843. 
Table 10. — Comparisons of the Thermometers with the Bulb free, and with the 
Bulb in a brass bar. 
Gottingen 
Thermometer. 
Difference. 
Mean Time. 
Ross. 
Adie. 
1844. 
d. h. 
Jan. 2 21 
30-9 
30-7 
0-2 
22 
31-3 
31-0 
0-3 
23 
31-9 
31-5 
0-4 
Jan. 
3 
0 
33-9 
33-0 
0-9 
1 
38-9 
37-6 
1-3 
2 
42-3 
41-0 
1-3 
3 
44-7 
43-0 
1-7 
4 
45-6 
44-0 
1-6 
5 
45-9 
44-5 
1-4 
6 
46-0 
44-9 
1-1 
7 
8 
46-1 
45-9 
45-0 
44-9 
11 
1-0 
11 
45-0 
44-3 
0-7 
34. In the adjustment of the instrument, the magnet is forced to a position at 
right angles to the magnetic meridian, by turning the arms of the torsion circle. 
As, in forcing the magnet from the meridian, the upper extremities of the wire will 
move through a greater angle than the lower extremities, the wires will be no longer 
vertical, and the magnet and appendages will be raised ; the forces producing equi- 
librium will, therefore, be the weight suspended endeavouring to attain the loAvest 
point, and the horizontal component of the earth's magnetic intensity acting on the 
free magnetism of the bar. 
35. If v be the excess of the angular motion of the arms of the torsion circle, 
or upper extremities of the wire, over u, that of the lower extremity or magnetic bar 
in moving the latter from the meridian, the equation of equilibrium will be 
2 
m X sin u — W-y sin v. 
m, X, W, a, and I being respectively the magnetic moment of the bar, the hori- 
zontal component of the earth's magnetic force, the weight suspended, the interval, 
and the length of the wires. The differential of this equation (» = 90 CN ) divided by 
it, gives 
A X 
= ii a cot v + t (Q + 2 e — e') 
A. 
it being the number of scale divisions from the zero, or scale reading when u = 90% 
a the arc value in parts of radius of one scale division, t the number of degrees 
Fahrenheit which the temperature of the magnet is above the adopted zero, Q the 
