Bowl-Diameter 8.5" (21.6cm) brass, expansion chamber and filler plugs at base. Inside of bowl unpainted with four black lubber lines on white strips which etend above verge glass onto raised verge ring. A brass azimuth circle is fitted which has sights mounted on a framework which is secured by a pin to the verge glass of the circle. The verge ring of circle is graduated to 360 degs. The sights consist of one prosm with two shades and the other a frame with sighting wire and dark glass rflector.
Card- Diameter 7.75" (19.7cm) white painted metal ring 1.5" (3.8cm) wide, with black markings, graduated in two rows to 360 degs. The outer now displaced by 180 degs to use for taking bearings. Attached to large metal float at centre.
The body of the instrument consists of a circular framework hung in gimbals and carrying the compass bowl. In the space between the upper and lower plates of the framework, 32 tapering soft iron rods are carried on cradles working in medial grooves. Below the bottom plate, a movable plate is fitted, having 3 slots set at varying angles. A screw pin securing each rod and its cradle passes through each slot and when the movable plate is rotated, the rods are moved inwards or outwards by the slots acting upon them. When at the extreme outwards position, the inner ends of the rods are concentric, and when at the extreme inwards position they form an ellipse around the compass centre and corect the quadrantal error. A pointer on gimbal ring operates on a scale on upper plate and indicates amount of movement. By means of rack and pinion below framework the whole system of rods can be rotated to correct coefficient E, a pointer on upper plate is used to read a scale engraved on gimbal ring. Seting screws are provided by which movable parts can be locked.
On wooden stand 17" x 6" x 1.25" ( 43.1 x 15.2 x 3.1 cm)