Sheraton, Thomas; Bensley, Thomas; Mathews, James; Bensley, Thomas [Bearb.]; Mathews, James [Bearb.]; Terry, George [Bearb.]; Jordan, Jeremiah Samuel [Bearb.]; Wayland, L. [Bearb.]: The Cabinet-Maker And Upholsterer's Drawing-Book: In Three Parts (London: Printed For The Author, By T. Bensley; And Sold By J. Mathews ... C. Terry ... J.S. Jordan ... L. Wayland ... And By The Author, 1793)

( 66 )

obferving, that if b, which is the end of the notched wood or
tramel hick, is moved gradually to g, the internal angle of the
fquare, then will the pencil point be at /, becaufe from b to the
pencil point is equal to half the long diameter: and again,
if a, at the notch, be gradually turned to the inner angle of
the fquare, then will the pencil point be at e, becaufe from a to
a is equal g e, half the fhort diameter.
I have already fhewn the method of drawing an oval by
the fedtor in Section II. page 38, and therefore I need not fay
any thing on it here.
Prob. XVIII. Fig. 30.
To find the center and two diameters of any Oval whofe
circumference is already given, and whofe center and diameters
are erafed or rubbed out.
Operation.—Let m I q g be the circumference of the oval.
Draw the right line 0 q at random, and draw m n any where
parallel to 0 q^ by means of two arches, as the figure fhews.
Second, Bifed: the line m n from its interfediion with the
circumference of the oval, as at r. Alfo bifed: 0 q in the fame

manner