39 s Ah Account of the Measurement 
it to bear against a screw passing through a head of metal be- 
neath that end. The extremity of the long screw is square, 
and has its place in a pipe attached to a mahogany rod, divided 
in the middle by a universal joint. One extremity of this rod is 
brought down, and received in a socket within convenient reach 
of the observer, who, looking at the image of the dot and wire, 
turns the rod, thus connected with the bent lever, and thereby 
gives motion to the plumb-line. 
The pivots of the sector’s axis are of bell metal, ground per- 
fectly true and smooth. They rest in Ys, firmly attached to the 
upper part of the frame. The method of uniting the plates car- 
rying those Ys, is as follows : at the upper part of the mahogany 
frame are four hollow strong cylinders of brass, which pass 
through the wooden work, and, at the same time, serve to con- 
nect very firmly the two sides of the upper part of the frame. 
These cylinders project about six inches beyond the surface of 
the wood, and have screws and nuts at their ends. 
The brass plates furnished with the Ys, have four holes in 
each of them, which answer to the ends of the screws, and are 
attached to the cylinders furnished with those screws, by the 
respective nuts. In the Ys, the pivots of the axis are placed; 
and, as a means of adjusting each Y is fixed to each plate, any 
position, within a certain limit, may be assigned to the sector 
and its axis. 
To prevent the pivots of the axis from moving to and fro in 
a sidelong direction, Mr. Ramsden adopted a contrivance for 
keeping them, at all times, in the same constant position in the 
Ys. This desideratum was not to be dispensed with; for, if the 
ends of the axis, from the thickening of the oil, or the accumu- 
lation of dust, should work laterally in their angles, the distance 
