The Sonograph
  The name of this device tells everything: it is designed to make sound visible. Sound waves are gathered in a funnel and  travel down the tube at the left. They cause a membrane to vibrate, and this, in turn, makes a small, light mirror, located in the middle of the circle of brass, vibrate. A beam of light reflected from the mirror thus oscillates up and down. The necessary time base is produced by reflecting the beam of light from a rotating mirror; this method was also used by the Manometric Flame.

   The instrument is in the collection at Virginia Military Institute, and was made by the L. E. Knott Apparatus Co. of Boston. It is listed at $25 in the 1916 Knott catalogue; the catalogue description includes wave shapes of a human voice pronouncing the vowels.

   This is a form of Phonodeik, a device invented by Dayton Clarence Miller (1866-1940) of the Case School of Applied Science about 1906. Prof. Miller used it to record the voices of scientific celebrities, including J. J. Thomson and Joseph Larmor.

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