J. J. Thomson and the Discovery of the Electron (1897)
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
In 1897, J. J. Thomson used a cathode ray tube to show cathode rays were negatively charged particles lighter than any atom.
Show
Deflecting the ray with electric and magnetic fields let Thomson calculate a charge-to-mass ratio, identical no matter which metal formed electrodes.
Watch for
The particle was not a smaller atom; being far lighter than any atom marked it a new subatomic constituent.