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Inventory no. 30371 - Former Display Label

English ELLIPTICAL TRAMMEL
18th century, and before 1759

Brass. Signed, "Josph, Jackson London"; undated.

This is an instrument for drawing ellipses. The T-shaped base, along the arms of which slide the supports controlling the drawing-arm, is fitted with two needle-points to prevent the instrument moving while in use. One half of an ellipse is drawn at a time; the position of the instrument being reversed in order to draw the other half. Supplied with the instrument are a pencil-holder, a pen, and a 'dry line' point. In the holder into which these fit is a small spring so that even contact with the drawing surface is maintained. There is a fine screw-adjustment attached to the holder.

Gunther (Early Science in Oxford, I, 138-9) quotes a letter from John Bird, the instrument-maker, which apparently refers to this instrument:
"To the Revd. Dr. Fanshawe Oxford
London 6th Jany 1759.

Sir,
I return'd your Instrument last Thursday by Parson's waggon. I might have sent it sooner, if I had not waited for an opportunity of consulting Dr Bradley about it, the result of which, was to put labels to the screws that are to be fasten'd, and eased, for the purpose you require ... As the Ink point (in this case) alters its position with regard to the line it draws, it was thought necessary to make two other points; one to carry a pencil, the other to draw what is called a dry line: the nut upon one of them serves for both, and in the socket where the points go, is a small worm spring, which will answer for all the points.

I am Sir your most obedient servt.

J. Bird."

Lent by Christ Church.

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