Brass Farey's ellipsograph dated 1817, in mahogany case
Farey's ellipsograph dated 1817 in mahogany case. An ellipsograph is used to draw ellipses, which consist of a combination of two circular motions. The drawing pencil is fixed in position in a central ring, which then revolves. At the same time, the ring is carried round in a circle, and the pencil traces the combination of these two paths.