The spinthariscope was a popular amusement at academic parties in the early 1900s, or so I am told. Recently they have become available again on eBay and maybe other places. Antique ones used radium, but modern ones sensibly use americium, which is much safer and is easily available in any smoke detector.
After about 10 minutes of rigorous dark adaption (absolutely no light allowed) you can clearly see a swarming glow on the zinc sulfide screen, each flash representing the decay of a single atom of americium and the subsequent striking of the released alpha particle into the screen. It's amazing.
Here is an article about spinthariscopes.
Source: eBay seller geoelectronics
Contributor: Theodore Gray
Acquired: 10 September, 2003
Text Updated: 11 August, 2007
Sample Group: Spinthariscopes