1) Obsolete technology 2) Optical device 
A stauroscope is an optical instrument used in determining the position of the planes of light-vibration in sections of crystals. The word comes from Greek for cross + scope. It was invented by Wolfgang Franz von Kobell in 1855. ...
instrument for studying structure of crystals with polarised light
• (n.) An optical instrument used in determining the position of the planes of light-vibration in sections of crystals.
Stau'ro·scope noun [ Greek ... a cross + -scope .] (Crystallog.) An optical instrument used in determining the position of the planes of light-vibration in sections of crystals. 
stauroscope An instrument for determining the position of the planes of vibrations in crystals.