Source : Webster's Revised Unabridged Dictionary (1913)

Geissler tube \Geis"sler tube`\ (Elec.)
   A glass tube provided with platinum electrodes, and
   containing some gas under very low tension, which becomes
   luminous when an electrical discharge is passed through it;
   -- so called from the name of a noted maker in germany. It is
   called also {Pl["u]cker tube}, from the German physicist who
   devised it.