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
Artificial mercury horizon with fitted leather carrying case, designed by Captain Christopher, provisionally patented in 1868 (No.2624), by the company of William Cary, 1868-1875. Consists of two black-lacquered steel mercury holders on three levelling feet, interconnected by a tube fitted with a stopcock. One is a storage reservoir with a valve to admit air and empty the mercury into the other, which is used for making observations and is fitted with a glass cover. A spare glass cover in a chamois leather pouch, and a lever pin for operating the stopcock (both stored in the glass-covered reservoir). Artificial mercury horizon. 1865-1875
