Reflecting goniometer

Goniometer \Go`ni*om"e*ter\, n. [Gr. ? angle + -meter: cf. F.
   goniom[`e]tre.]
   An instrument for measuring angles, especially the angles of
   crystals, or the inclination of planes.
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   {Contact goniometer}, or {Hand goniometer}, a goniometer
      having two movable arms (ab, cd), between which (at ab)
      the faces of the crystals are placed. These arms turn
      about a fixed point, which is the center of the graduated
      circle or semicircle upon which the angle is read off.

   {Reflecting goniometer}, an instrument for measuring the
      angles of crystals by determining through what angular
      space the crystal must be turned so that two rays
      reflected from two surfaces successively shall have the
      same direction; -- called also {Wollaston's goniometer},
      from the inventor. Goniometric
    

Reflecting \Re*flect"ing\, a.
   1. Throwing back light, heat, etc., as a mirror or other
      surface.
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   2. Given to reflection or serious consideration; reflective;
      contemplative; as, a reflecting mind.
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   {Reflecting circle}, an astronomical instrument for measuring
      angless, like the sextant or Hadley's quadrant, by the
      reflection of light from two plane mirrors which it
      carries, and differing from the sextant chiefly in having
      an entire circle.

   {Reflecting galvanometer}, a galvanometer in which the
      deflections of the needle are read by means of a mirror
      attached to it, which reflects a ray of light or the image
      of a scale; -- called also {mirror galvanometer}.

   {Reflecting goniometer}. See under {Goniometer}.

   {Reflecting telescope}. See under {Telescope}.
      [1913 Webster]