12 
Dr. Fordyce's Account 
therefore the centres of the screws L L which form the point I, 
fig- i, in perpendicular height. Then the screws L L, fig. 2, 
are to be screwed home, the screw G, fig. 3, is to be loosened 
so as to leave the tube I I, which is the same in both figures, 
perfectly free and untouched by any of the apparatus except- 
ing at the point I, the fixed point. The same thing is to be 
done, only in the reverse, if the clock be found to go too fast 
in a greater degree of heat, too slow in a greater degree of 
cold. 
In the clock which I have constructed, the bar BC, fig. 1, 
is considered as inflexible. If it were flexible, a weight hung 
at C would occasion it to fall lower, and in consequence bring 
the rod CD lower, and a greater part of it below the point E; 
thus the pendulum would be lengthened. It is therefore ne- 
cessary to make this rod as inflexible as possible ; for this 
reason it is made of a strong brass bar, HK, fig. 3> which is 
farther strengthened by a brass bar LK, supported by the up- 
right HL. 
If a weight were hung at K, it would tend to draw the tube 
I out of the perpendicular towards K. To prevent this, ano- 
ther bar HM is carried exactly opposite, so that MHK shall 
form the same bar, the under surface of which is paral- 
lel to the horizon. At the end of this bar M, is appended a 
weight O, so that, supposing the line LH to be the axis of the 
tube I I continued, and perpendicular to the horizon, then the 
whole of the weight on the side of LH towards M, shall be 
equal to the whole of the weight on the side of LH towards 
P. P is the head of a screw, to the centre of which the rod 
CD, fig. 1, is attached ; this screw passes through the end of 
the bar HP, in the same manner as the wire sustaining the 
