A 17th C. version of a simple quadrant missing its plumb bob, but with the two sighting pinholes clearly in evidence at the apex and to the right. This example represents the late evolutionary period of such instruments. It is engraved brass whereas earlier versions were of wood and it performs several functions which the earliest quadrants did not. The upper portion is engraved with a "shadow square" for use as a sundial. At the bottom it is divided to single degrees to allow for sighting the altitude of the sun or stars. Across the face of the instrument is a depiction of the celestial hemisphere showing major stars, the Equator, and Tropic of Cancer. Below these are engraved the months of the year, accounting for seasonal changes in the sun's declination and providing a Zodiacal calendar. This form of quadrant was also known as a "Gunter quadrant" after Edmund Gunter who described it in 1623. (Private collection)