Ernest Rutherford (1871-1937) discovers that uranium radiation is composed of positively charged alpha particles and negatively charged beta particles.
Citation:
Editors. "Uranium radiation explained by Rutherford".
The Literary Encyclopedia. First published 01 May 2009
[http://www.litencyc.com/php/stopics.php?rec=true&UID=6384, accessed 26 May 2013.]