An English Altitude Theodolite, William Wilton, Cornwall, circa 1830, circular plate with extended arms to carry open sights, in the centre is a silvered compass, underneath a glazed case, flanked by two spirit levels and a scale divided into quadrants of 0-90, corresponding with each point of the compass, needle locking device, and a raised scale of 0-360, glass cover. The semicircle above is engraved on the arc with 0-90-0 which is engraved to its outer edge. An index arm is mounted at the centre of the semi-circle, with vernier and carrying the sighting arm with a bubble level mounted centrally between the sights. Catalogue note: William Wilton is listed as an horologist and instrument maker at St. Day, Cornwall, between 1830 - 1851, and at Market place, Camborne from 1852 - 1856., an identical instrument by William Wilton was displayed in the Captain Cooks Exhibition at the Science Museum, Melbourne