1 6 
Dr. Fordyce's Account 
been laid before this learned Society ; therefore I shall only 
mention briefly, that the frame of Mr. Whitehurst's machine 
was formed of two pieces of very clean well seasoned deal, to 
which was fixed the apparatus for rendering the wire flexible of 
which his pendulum was formed at the point O, fig. 4, but there 
were no semicylindric pieces ; the two square pieces came toge- 
ther, so as to make the top of the pendulum at their under sur- 
face ; these pieces could be brought away from one another by the 
screw Y, so as to leave the wire free. The use of this was, by 
the screw L, fig. 4, to adjust the pendulum to its proper length, 
which has in this apparatus a considerable advantage, as it is 
not necessary, in the form I have given to this apparatus, to 
stop the clock in order to adjust it. These pieces of wood are 
mortised into a transverse piece of deal at the top and at the 
bottom firmly. Before I attempted to make a very perfect 
machine on these principles, I resolved to try how far this 
frame of wood might serve to connect the points I and E, fig. 
1, and procured the apparatus for altering the point I, screwed 
on to one of these perpendicular pieces of wood on one side, 
and to the other on the other side. The pendulum itself serves 
as a plummet to place them perpendicular. In Mr. White- 
hurst's machine the screw at L, fig. 4, went through a piece of 
brass, and rested upon it, fixed to the top of the clock-case. 
But in my construction of it, when the length of the rod IB, 
fig. 1, is adjusted, the clock has nothing to do with the clock- 
case, excepting with that part of the wooden frame which 
connects the point I with the point E, fig. 1. If I had been, 
or were to construct a machine for this purpose ab origine, in- 
stead of these two pieces of fir, I should employ a solid piece of 
brass, and make two cylindric cavities into it, parallel to one 
