Brass sector by George Adams, 1756-1760

Nine inch brass sector, by Adams; engraved "Improv'd and made by Geo. Adams, Mathm. Inst. Maker to His Royal Highness, George Prince of Wales, London", in fishskin case. Sectors were used in calculations involving proportion. They contain logarithmic and trigonometrical lines, many of which radiate from the centre of the hinge.