Graduations-Circle graduated to 360 degs and 1-60. A circle around both sight vanes is graduated to 200. Two lines which radiate downwards from upper compass are graduated, one 0-100, the other 0-20. A cirle around lower compass is graduated to 12 hours. The alidade has a fiducial edge at each end. The circle is mounted on a wooden base 6.4" (16.2cm) dia., with a brass suspension screw at top.
Sights-Two sight vanes 0.9" (2,4cm) long are mounted on circle, each having a vertical slit. Two sight vanes 0.9" (2.4cm) long are mounted on alidade, each having a vertical slit.
Compass-Two compasses; each 1.25" (3.2cm) dia. One mounted at centre of upper half of instrument, the other at the centre of the lower part. Each fitted with a blued steel needle 1.15" (2.9cm) long, with a brass pivot cap at centre. No graduations except for an arrow N-S inscribed on base of each bowl.