phosphoroscope

Century Dictionary and Cyclopedia

1. n. An instrument for. measuring the duration of evanescent, phospho' resceuce in different substances. It consists of a hollow disk within which is placed the object to be tested. The disk is geared with multiplying-wheels so that it can be rotated at any desired speed, and is so perforated on opposite sides that the substance placed within it is alternately exposed to a light placed behind the disk and to the eye.
2. n. A philosophical toy consisting of glass tubes containing different phosphorescent substances and arranged in a box. When exposed to sunlight or strong artificial light, and afterward put in a dark place, the tubes glow with lights of different colors.

Wiktionary

1. n. Any of several devices used to measure phosphorescence, and to distinguish it from fluorescence

GNU Webster's 1913

1. n. An apparatus for observing the phosphorescence produced in different bodies by the action of light, and for measuring its duration.