Bowl- Black painted brass, filler plug at side, expansion chamber at base. Inside of bowl painted white, with four black painted lubber lines. Verge glass has small hole at centre (possibly to take a shadow pin). An azimuth circle of unusual type is fitted in whcih bearings are taken at right angles to line of sight through an aperture on prism frame. Two prisms are fitted, one for sighting object and partly for reflecting the line of sight through the second prism to edge of card. One coloured shade is fitted.
Card- Diameter 7.75" (19.7cm) ring 1.5" (3.8cm) Mica, covered with linen, white with black markings, graduated quadrantally in degrees and to 1/4 points. Card attached to white painted float dome by two long needles carried below float and attached to card by wires.
Needle- Two needles of circular section 7.75" (19.7cm) long. Said to contain bundles of thin steel wires, according to Ritchie plan.
Pivot-Unsighted. Possibly of inverted type, with a jewel cup contained in float dome.