Cubitt's Ellipsograph with passe-partout framed drawing

In this instrument, devised by W. Cubitt in 1817, one slot is enlarged to 4 ½ inch width, the slider and pin being in the form of a brass ring, as in Farey’s instrument.

A groove in this ring carries a slider, to which is attached a pin moving, when an ellipse is described, in a slot at right angles to the direction of motion of the centre of the ring. The pin can be adjusted and clamped eccentrically on the ring, to suit the proportions of the ellipse required. A bar attached to the ring is carried underneath and the drawing-pen can be clamped in any position along the bar. By means of a milled-headed screw the pen can be lifted from the paper when not in use.