E *98 3 
H is a Leader exattly of the fame Form and Dimen- 
sions with the former 5 but the Chain faftened to the 
Pulley on its Axis is hook'd to the Standard Bar*, 
The Line fatten'd to the End of this Leaver, after being 
wound round a Cylinder, to which the moveable Plate 
fixed, paffes over a fmall Pulley, and has a Weight 
hung to the End of it 5 or rather the fame Line palling 
under a Pulley, to which the Weight is hung, has its 
other End faftened to the Leaver F : Thus one Weight 
lerves for both Leavers, as in the Figure. 
From this Defcription it is plain, that whenever the 
Bar E is lenghten'd, it gives Liberty to the Weight to 
draw the Leaver F upwards by its Aftion on the 
Spring G; and the Index will, at the fame time, by 
Means of the Silk Line, be carried forward in the 
Circle; and as the Bar fhortens, it will return back 
again ; the fame Motion will be communicated to the 
Standard Bar. 
The Lengthening the Bar the of ail Inch, will 
carry the Index once round the Brafs Circle, which 
is divided into 360 Degrees; therefore, if the Metal 
lengthens the 7200th Part of an Inch, the Index will 
move one Degree. 
To make an Experiment with this Inftrument , lay 
a Bar of any kind of Metal, as E, on the Standard 
Bar; then heat the Standard Bar to any Degree of 
Heat with a Lamp, and mark the Degree of its Expan- 
fion as marked by the moveable Plate : Obferve alfo 
the Degree of Expanfion of the Metal E, by the Heat 
* N. B. The Chain to the former Pulley being fatten'd to a Spring, and 
not diredlly to the Metal E, is only for the more eafy Ihifting the 
Metals. 
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