\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.