Source : Webster's Revised Unabridged Dictionary (1913)

Hittorf tube \Hit"torf tube\ (Elec.)
   (a) A highly exhausted glass tube with metallic electrodes
       nearly in contact so as to exhibit the insulating effects
       of a vacuum. It was used by the German physicist W.
       Hittorf (b. 1824).
   (b) A Crookes tube.