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
