Polished brass frame, with two wooden handles, one of which is secured to a detachable U-shaped bracket. A very rare example of an English made "Borda" repeating, reflecting circle for measuring the distances involved in the "lunar type" method of finding longitude. Chevalier de Borda's repeating circle, invented c.1772 was an improved form of tobias Mayer's original circle of c.1755 and is described in his "Description et Usage du Cerle de Reflexion, Paris 1787".
Brass scale from 0° to 720° by 30'. Two verniers by 1', zeros at right. First index arm carries index glass with screw adjustment, second index arm carries horizon glass with screw adjustment. Tangent screws and clamp screws on the back of the index arms. Three detachable rectangular index shades (red, red, green) two square detachable horizon shades (both red). Index and horizon glass adjustment by screws. Two telescope brackets, perpendicular adjustment by milled knobs. Telescope (115 mm), inverted image, two cross wires. Adjusting pin. Diameter 10.75'' (273 mm). In a square fitted wooden box lined with green paper, and containing in the lid a printed London trade label over which a paper was stuck with in MS 'Patent Reflecting-Circle', and a blank brass plate on the lid.