The Collaborative International Dictionary of English v.0.48:

Cymoscope \Cy"mo*scope\, n. [Gr. ? wave + -scope.] (Elec.)
   Any device for detecting the presence of electric waves. The
   influence of electric waves on the resistance of a particular
   kind of electric circuit, on the magnetization of steel, on
   the polarization of an electrolytic cell, or on the electric
   condition of a vacuum has been applied in the various
   cymoscopes.
   [Webster 1913 Suppl.] Cymose