( ?’0 ) 
of the Tube, when the Metal is in it, which is equivalent 
to about two Pound at where the Line is faflened* 
In great Elevations of the Objed above the Horizon, the 
Line is not carried fo far as the Pointy, but is faften’d 
a little above the Pulley, to a light fquare Stick, 
having at one End a Hook, by which it takes hold of 
the Staple g. This is done, that the Springynefs of the 
Line may not continue a vibrating Motion in the Tube, 
(when any thing happens to fhake the Inftrument) and 
make the Objeft appear to tremble. The lower Part 
of the Stick refts againft the end of the Arm, and by 
its flight Fridion contributes to the fameEffed. 
The other Peg, ss, is fo plac’d, that it may be con- 
veniently reached by one Hand of the Obferver, while 
the other is employed about the Peg Y : It regulates the 
Horizontal Motion of the Tube, by means of a Line, 
which being wound about the Peg at one End, paffes 
by another fmall Pulley placed clofe by the Side of the 
aforementioned one in an Horizontal Pofture (not to be 
feen in the Figure) and is hung on a Pin driven into 
the little HeadK. It is aded againft by two Springs, m 
andw Fig, 5. placed in the Box, III, one on each Side 
of the turning Pillar ^ that on the right Hand, w, draws 
the right Side of the Pillar forward, by a very ftrong 
Line, which being faftened to the Head of the Spring, 
palTes round the back Part of the Pillar to a Pin, at P, 
by which it is drain’d to its due Strength, The Spring 
on the Left Hand », draws the Left Side of the Pillar 
backwards in the fame manner. Thefe Pins are plac’d 
on the Pillar a little higher than the Tops of the Springs, 
that being drawn a little downwards, as well as turn’d 
round its Axis^ the Pivot in its Bottom may not be 
raifed out of the Hole in the Brafs Plate, when the Reft 
bears hard againft the Rollers at the End of the Arm. 
&ich of thefe Springs draws with a Force equal to about 
■ 18 
