What is "spinthariscope"

Spinthariscope \Spin*thar"i*scope\, n. [Gr. spinqari`s spark + -scope.] A small instrument containing a minute particle of a radium compound mounted in front of a fluorescent screen and viewed with magnifying lenses. The tiny flashes produced by the continual bombardment of the screen by the [alpha] rays are thus rendered visible. -- Spin*thar`i*scop"ic, a.

n. an early device used for observing individual nuclear disintegrations

A spinthariscope is a device for observing individual nuclear disintegrations caused by the interaction of ionizing radiation with a phosphor (see radioluminescence) or scintillator.