Double sounding sextant made by Thomas Jones, London, about 1830. Two polished brass sextant frames and limbs connected parallel to each other by pillars and a brass plate; two wooden handles, one the front the other on the back of the frames. Signed on the limb of the upper sextant: Thomas Jones 62 Charing Cross London. Marked on the crossbar of the upper sextant: D.170. Two inlaid silver scales, each from -2° to 143° every 20', measuring to 128°. Two silver verniers both to 30". Two index arms, the tangent screw and clamping screw is on top of the upper arm; the lower tangent screw and clamping screw are on the back of the lower frame. No shades. Adjustment of the index and horizon glasses by square-headed screws and a detached key (not found). The magnifier on the upper sextant is on a 80-mm swivelling arm; that on the lower sextant is on a 100-mm swivelling arm mounted on the back of the frame. Threaded telescope bracket in two parts, fitted for correcting collimation error; the bracket is fixed between the two frames. Telescope (165 mm) with a shade (red), erect image. Sight tube (155 mm). The limb of the lower sextant is fitted with a greatest angle clamp (see notes). Box not seen, WMB. A trade label for Thomas Jones, London taken from the box. Double sounding sextant. 1825-1835
Pocket double box sextant of 2½-inch radius, designed by Captain Christopher George (Trade Mark No.31) with two circular lacquered brass plates and two lids, by the company of, William Cary, Strand, City of Westminster, London, England, 1835-1845. Fitted with two Inlaid silver scales 135° and 123° (-5° to 150°) with 30 arc-minute divisions and a silver vernier with 1 arc-minute divisions and index arms rotated by milled knobs on the upper and lower plates. The index glass is fixed with adjustment for the horizon glass and a single lens magnifier is hinged on a swivel arm (40 mm) with choice of large and small pinholes Double box sextant. 1835-1845
