Emily Dickinson Lexicon

PO-LEM'O-SCOPE, n. [Gr. πολεμος, war, and σκοπεω, to view.]

An oblique perspective glass contrived for seeing objects that do not lie directly before the eye. It consists of a concave glass placed near a plane mirror in the end of a short round tube, and a convex glass in a hole in the side of the tube. It is called opera-glass, or diagonal opera-glass. – Encyc.