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I. The Defcription and Marnier of ujing an 
Inftrument for meafuring the Degrees 
of the Expanfion of Metals by Heat . 
By Mr. John Ellicott. 
See the Fig. prefix'd. 
A A is a flat Plate of Brafs, which, for farther 
* Strength, is fcrewed down to a thick Piece of Ma- 
hogany : Upon this Plate are fcrewed three Pieces of 
Brafs, two of which, marked BB, ferve as Supports 
for the flat Iron Bar C 5 and which, on account of its 
Ufe, I (hall call the Standard Bar. The upper Part 
of the third Piece of Brafs is a Circle about three 
Inches Diameter, divided into 360 equal Parts or De- 
grees : Within this Circle is a moveable Plate, divided 
likewife into 360 Parts, and a fmall Steel Index. The 
Brafs Circle in the Fig. is marked D, and the moveable 
Plate d. Upon the Standard Bar the Bar of Metal is 
laid, on which the Experiment is to be made, as E. - 
F is a Leaver 2 \ Inches in length, fattened to an 
Axis, which turns in two Pieces of Brafs ferew'd to 
one of the Supports marked B: To the End of this 
Leaver is fattened a Chain, or Silk Line, which, after 
being wound round a fmall Cylinder, to which the 
Index in the Brafs Circle D is fattened, pafles over a 
Pulley, and has a Weight hung to the End of it : Upon 
the Axis, to which the Leaver is fixed, is a Pulley, ^ of 
an Inch Diameter, to which a Piece of Watch-chain 
is fattened ; the other End of this Chain is hook'd 
to a ftrong Spring, marked G, which Spring bears 
againft one End of the Metal E. 
Q,q 
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