Pierre Vernier

Inventor of the instrument which bears his name, b. at Ornans, Franche-Comte, c. 1580; d. there, 14 Sept., 1637. His father was his teacher in science. He became captain and castellan, for the King of Spain, of the castle at Ornans, and councillor and director general of moneys in the County of Burgundy. At Brussels, 1631, he published and dedicated to the Infanta, the treatise "La construction, l'usage, et les propriétés du quadrant nouveau de mathématiques", describing the ingenious device on which his fame now rests. To a quadrant with a primary scale in half degrees Vernier proposed to attach a movable sector, thirty-one half degrees in length but divided into thirty equal parts (each part consisting then of a half degree plus one minute). In measuring an angle, minutes could be easily reckoned by noticing which division line of the sector coincided with a division line of the quadrant. Christopher Clavius had mentioned the idea but had not proposed to attach permanently the scale to the alidade. The name vernier , now commonly applied to a small movable scale attached to a sextant, barometer, or other graduated instrument, was given by Lalande who showed that the previous name nonius, after Peter Nunez, belonged more properly to a different contrivance.