altiscope

Century Dictionary and Cyclopedia

1. n. An instrument consisting of an arrangement of lenses and mirrors in a telescopic tube, extensible vertically, by means of which it is possible to look over objects intervening between the observer and the object to be seen. When the sections of the tube are extended, the view is received upon an upper mirror placed at an angle of 45°, and reflected thence down the tube to a lower mirror, where it is seen by the observer.

Wiktionary

1. n. An arrangement of lenses and mirrors making it possible to see around obstructing objects.

GNU Webster's 1913

1. n. An arrangement of lenses and mirrors which enables a person to see an object in spite of intervening objects. Since the early 1900's, most commonly called periscope.