Ellipsograph, brass, in mahogany case with accessories, signed Troughton & Simms, London, mid 19th

Elliptographs are machines for drawing small ellipses, the shapes seen when circles are viewed in perspective. They became popular during the first half of the 19th century as the demand from engineers and architects increased.

An example of this kind was displayed at the Great Exhibition of 1851. It was designed by Airy, the Astronomer Royal. The instrument has a circular trammel supported by three pillars which constrains the movement of the pen on a knuckle joint between roller-castors. There is also a ‘T’ square, a rectangle, and two triangular set squares supplied in a fitted box.