eido-, eid-; ido-, id-

An optical instrument, consisting of from two to four reflecting surfaces placed in a tube, at one end of which is a small compartment containing pieces of colored glass: on looking through the tube, numerous reflections of these are seen, producing brightly-colored symmetrical figures, which may be constantly altered by rotation of the instrument.

Of or belonging to the kaleidoscope; exhibiting brightly colored or continually varying figures like those seen in the kaleidoscope.

An instrument invented by Prof. A. E. Dolbear (West Virginia), consisting of a tube closed at one end by a tense membrane, having attached to its center a small mirror, to show the musical vibration caused by speaking or singing at the open end.

1. An instrument for exhibiting the color-figures produced by the action of sound-vibrations upon a thin film, e.g. of soap-solution.
2. An instrument for studying the motions of sounding bodies with optical methods.