Sextant, an instrument used in navigation (sometimes also in land-surveying) for measuring the altitudes of celestial bodies and their angular distances; consists of a graduated brass sector, the sixth part of a circle, and an arrangement of two small mirrors and telescope; invented in 1730 by John Hadley.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Seward, William Henry * Seychelles