Graduations-Semicircle graduated 0-180 degs, 180-0, with a diagonal scale. The alidade 12.5" (31.8cm) long, has a fiducial edge at each end (the left hand edge has a square frame with a thread which is observed through a glass covered aperture in top of a brass box which extends from the pivot to end of alidade). A straight edge 14.6" (37cm) long at lower part of instrument. A ball and socket head and brass plate 4 x 3.5" (10.1 x 8.9cm) are attached to back of instrument.
Sights-A telescope 16.5" (41.9cm) long, 1" (2.5cm) dia, inverting with cross wires, fitted with two sight vanes on top; at eyepiece end a sight vane 1.9" (5cm) long with a vertical slit, the other an adjustable rectangular aperture (complete with brass sighting strip), mounted on brass bracket at centre of alidade. A telescope 16.15" (41cm) long, 1" (2.5cm) dia, inverting, mounted on underside of straight edge.
Compass -Dia 3" (7.6cm) mounted at centre of instrument. Fitted with blued steel needle in form of arrow 2.5" (6.5cm) long, with a brass pivot cap at centre. Graduated to 16 points and to 360 degs.