Vernier

—A small movable scale invented by Pierre Vernier in 1631, and used for measuring a fractional part of one of the equal divisions on the graduated fixed scale. The vernier consists in its simplest form of a small sliding scale, the divisions of which differ from those of the fixed primary scale. On the scale of the tool is a line of graduations divided into inches and numbered 0, 1, 2, etc., each inch - being divided into ten parts, and each tenth into four parts, making forty divisions to. the inch. On the sliding jw is a line of divisions of twenty-five parts, numbered 0, 5, 10, 15, 20, 25, The twenty-five divisions on the vernier correspond, in extreme length, to twenty-four divisions, or 7# of an inch, on the scale; each division — on the vernier is, therefore, of 3y Or tovo of an inch shorter than the corresponding division on the scale. If the vernier be moved until the line marked 0 on the vernier coincides with that marked on the scale, then the next two lines to the right will differ from each other by ypo of an inch: and the difference will continue to increase qoo of an inch for each division, until the line 25 on the vernier coincides with a line on the scale.