name which was not many years ago given to the common device for subdividing the arcs of quadrants and other astronomical instruments, from the persuasion that it was invented by Nonius or Nunez, of whom some account has been given in the preceding article. The generality of astronomers of the present age transferring the honour of the invention from Nunez to Peter Vernier, a native of Franche Comte, have called this method of division by his name. (See Vernier.) Mr Adams, however, in his Geometrical and Geographical Essays, has lately shown that Clevis the Jesuit may dispute the invention with them both. The truth seems to be, that Nunez started the idea, Clevis improved it, and Vernier carried it to its present state of perfection. The method of Nunez, described in his treatise De Crepulculis, printed at Lisbon 1542, consists in describing within the same quadrant 45 concentric circles, dividing the outermost into 90 equal parts, the next within into 80, the next into 88, &c. till the innermost was divided into 46 only. On a quadrant thus divided the plumb line or index must cross one or other of the circles very near a point of division; whence, by computation, the degrees and minutes of the arch might be easily ascertained. This method is also described by Nunez in his treatise De arte atque ratione Navigandi, where he would fain persuade himself, that it was not unknown to Ptolemy. But as the degrees are thus divided very unequally, and as it is very difficult to attain exactness in the division, especially when the numbers into which the arches are to be divided are incomposite (of which there are no less than nine), the method of diagonals, first published by Thomas Digges, Esq. in a treatise entitled Ayle seu facie mathematicae, printed at London in 1573, and said to be invented by one Richard Chenefler, was substituted in its room. Nonius's method was, however, improved at different times and by different persons; and it must be acknowledged, that if Vernier saw either the original or any of the improvements (and there can be little doubt of his having seen them all), his merit is only that of having applied to an useful practical purpose the speculative invention of another person.