As the β particles emitted by the radio-active elements are analogous to the α particles, inasmuch that they may be considered as parts of the disintegrated atom, and not in any sense true rays, I ...

The first method of counting atomic particles was by “scintillations.” Using a microscope, early atomic physicists counted the tiny flashes of light that are made by particles from radium as they hit ...

Hewish, A., Scott, P. F., and Wills, D., Nature, 203, 1214 (1964).