[1] : The Collaborative International Dictionary of English v.0.48

vernier \ver"nier\, n. so named after the inventor, pierre
   vernier.
   a short scale made to slide along the divisions of a
   graduated instrument, as the limb of a sextant, or the scale
   of a barometer, for indicating parts of divisions. it is so
   graduated that a certain convenient number of its divisions
   are just equal to a certain number, either one less or one
   more, of the divisions of the instrument, so that parts of a
   division are determined by observing what line on the vernier
   coincides with a line on the instrument.
   1913 webster

   vernier calipers, vernier gauge, a gauge with a graduated
      bar and a sliding jaw bearing a vernier, used for accurate
      measurements.

   vernier compass, a surveyor's compass with a vernier for
      the accurate adjustment of the zero point in accordance
      with magnetic variation.

   vernier transit, a surveyor's transit instrument with a
      vernier compass.
      1913 webster
see also:
vernier calipers vernier gauge vernier compass vernier transit 

Vernier >> V Words
Vernier, definition of term: Vernier
vernier_pag1.html

Compass >> C Words
Compass, definition of term: Compass
compass_pag1.html

Vernier Scale >> V Words
Vernier Scale, definition of term: Vernier Scale
vernier+scale_pag1.html

Compass Point >> C Words
Compass Point, definition of term: Compass Point
compass+point_pag1.html