Stereoscope, a simple optical apparatus which, when two photographs of an object taken from slightly different standpoints (so as to secure the appearance it presents to either eye singly) are placed under its twin magnifying lenses, presents to the eyes of the looker a single picture of the object standing out in natural relief.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Steppes * Sterling, John