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

compasses \com"passes\, n., pl.
   an instrument for describing circles, measuring figures,
   etc., consisting of two, or rarely more, pointed branches,
   or legs, usually joined at the top by a rivet on which they
   move.
   1913 webster

   note: the compasses for drawing circles have adjustable pen
         points, pencil points, etc.; those used for measuring
         without adjustable points are generally called
         dividers. see dividers.
         1913 webster

   bow compasses. see bow-compass.

   caliber compasses, caliper compasses. see calipers.

   proportional, triangular, etc., compasses. see under
      proportional, etc.
      1913 webster
see also:
dividers bow compasses bow-compass caliber compasses caliper compasses calipers 
proportional triangular compasses 

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

calipers \cal"ipers\, n. pl. corrupted from caliber.
   an instrument, usually resembling a pair of dividers or
   compasses with curved legs, for measuring the diameter or
   thickness of bodies, as of work shaped in a lathe or planer,
   timber, masts, shot, etc.; or the bore of firearms, tubes,
   etc.; -- called also caliper compasses, or caliber
   compasses.
   1913 webster

   caliper square, a draughtsman's or mechanic's square,
      having a graduated bar and adjustable jaw or jaws.
      --knight.

   vernier calipers. see vernier.
      1913 webster
see also:
caliper compasses caliber compasses caliper square vernier calipers vernier 

Compasses >> C Words
Compasses, definition of term: Compasses
compasses_pag1.html

Caliper >> C Words
Caliper, definition of term: Caliper
caliper_pag1.html