Ebony and brass octant.

Octant made by John and Edward Troughton, London, about 1800, for Sir George Shuckburgh, Bart. (1751-1804). Ebony frame and limb with a brass index arm and fittings; inlaid ivory plates on the crossbar and on the back of the frame. Signed at the bottom of the index arm: Troughton London. Inlaid ivory scale from -2° to 101° every 20', measuring to 90°. Ivory vernier to 1', zero at the right. The tangent screw and clamping screw are on the back of the index arm. Three shades (two red, one green); no horizon shades. Index-glass adjustment by screw; adjustment of the horizon glass by screw, lever, wing nut and a milled clamping screw. The sight vane has two pinholes and a swivelling shade (red). A pencil or screwdriver is missing from the crossbar. In a stepped oak keystone box, painted brown on the outside. Trade labels (taken from the box) for J. and E. Troughton, 136 Fleet Street, London (1788-1804) and for Ripley's, Mill Place, Commercial Road, London.