The Probert Encyclopaedia of Science & Technology

PERISCOPE

A periscope or altiscope is an instrument consisting of an arrangement of mirrors in a vertical framework, by means of which a person is enabled to overlook an object (a parapet, for instance) intervening between himself and any view that he desires to see, the picture of the latter being reflected from a higher to a lower mirror, where it is seen by the observer/
Research Periscope