Knowing nothing of Newton's quadrant, a later Fellow of the Royal Society, John Hadley (who had been working to improve the reflecting telescope), constructed a seaman's quadrant on similar principles.
Ukungazi nto ngesahlulo sesine sesangqa sika Newton, kamva umfana wasebukumkanini uJohn Haldley (owasebenza ukuphuhlisa isibonakude sokukhanyisa) wokha isahlulo sesine sesangqa sendoda yaselwandle esinemithetho eyeleneneyo.