Maker's Name: 
Solmon Marks and Co, Cardiff
Where made: 
25 × 24 × 11 cm

Brass sextant with wooden handle and finely engraved silver scale. The mirrors and filters are present but the telescope is missing.

Light from a celestial body such as the Sun or a star is reflected by a mirror attached to a moveable arm, through a mirror which also allows the horizon to be sighted simultaneously.

By bringing the image into coincidence with the visible horizon it is possible to measure the elevation of the body. Using an almanac and an accurate clock it is then possible to determine the position of the observer on the Earth's surface. This was the standard method of navigation from about 1800 until about 1980.