{Contact, 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.