Discovery of the electron: commentary on J. J. Thomson's classic paper of 1897

The discovery over 100 years ago that cathode rays were composed of negatively charged corpuscles–subsequently named electrons–was an historic event in the development of science, demonstrating for the first time that particles smaller than atoms existed and initiating other investigations into the nature of matter, as well as marking the beginning of the electronics industry. The research investigations of J. J. Thomson, leading up to the crucial experiments identifying the particle and determining its charge-to-mass ratio as reported in the Philosophical Magazine, are here described.