Octant, attributed to John Hadley ( British 1682-7744) ca 1740 Wood, Brass, Ivory. 17 1/8 inch radius, Photo courtesy of Seaport Museum, Philadephia. Gift by Austin B. Hepburn
This octant is believed to have belonged to John Barry (1745-1803), the first naval captain appointed by President Washington and remembered as the Father of the American Navy. Made before he was born, the octant would have come to Barry secondhand; either purchased by him on the cheap as a budding captain or gifted by a mentor. It is said to have been used by him while a Continental Navy captain aboard the ships Lexington and Alliance, among others, and also on a voyages he subsequently made to China.
Octants were used for celestial navigation and measured the angles of the sun above the horizon to find the latitude position of the ship. Almost simultaneously invented by Philadelphian Thomas Godfrey (in 1730) and Englishman John Hadley (in 1731), both of whom were recognized by the Royal Society, the octant allowed for a greater degree of navigational accuracy than its predecessor, the quadrant, and increased the reliability of ship arrivals.