of a new Pendulum. 13 
weight O passes through the end of the bar HM at N. The 
uses of this screw are to be seen in fig. 4, where HK represent 
the end of the bar HK, fig. 3, through which the screw A 
passes. The head of this screw P is toothed and divided. To 
the teeth there is a catch at K, which allows it to be turned 
backwards and forwards with a tolerable force, but keeps it in 
the same place until that force be applied to it. The upper part 
of the screw C, fig. 4, is a cylinder, which passes through a cy- 
lindric hole in the end of the bar HK, fitted to it so as to allow 
of being turned round without shaking. The screw itself passes 
through a female screw at D in the frame EF . 
This frame, as well as the screw itself, is made of brass, 
and consists of a bar EF, which is perpendicular to the hori- 
zon ; from which arise two pieces GG and EL, at right angles, 
therefore parallel to the horizon. In the upper piece EL is a 
female screw, through which the screw A passes ; so that the 
head P, being turned round, will raise the frame EF or de- 
press it. In the bottom part GF there is a slit MM, through 
which the rod NO passes. This rod passes through a piece of 
brass PP at Q, where it is fixed, so that by screwing forward 
the screw A, the point Q, and the rod NO consequently, will be 
raised up, and e contra. The point Q is placed exactly under 
the centre of the screw A. 
This point O is to. be considered as the point C, fig. 1. 
For although in fact the part of the rod HK where the screw 
A passes, and rests upon the end of the rod HK, be the point 
C, fig. 1 ; yet if a part of the tube I I, fig. 3, at the point C be 
taken at an equal height with (), fig. 4, as they are both of brass, 
both will expand equally. If the whole should be heated, the 
expansion of CH, fig. 3, will raise up the bar HK, and the ex^ 
