1700-1782

American mathematician and instrument maker who invented the double-reflecting quadrant (1730), which evolved into the modern sextant. John Hadley invented an almost identical instrument and published his work in 1730. A priority dispute arose, but the convenience of Hadley's design for ship-board use made his the instrument of choice for navigators. Godfrey published almanacs (1729-36), worked on mathematical and navigational problems, and took astronomical observations used to fix the longitude of Philadelphia.