Letter from Sir Joseph J Thomson, English physicist , 1924.
© Science Museum / Science & Society Picture Library
Back page of letter from Sir Joseph J Thomson (1856-1940) to Colonel Lyons, Director of the Science Museum, refering to the electron tube, 21 January 1924. Thomson studied sciences at Trinity College, Cambridge. After graduating, he continued to work at the university and in 1896 began experiments on cathode rays. Thomson showed that cathode rays were particles with a negative charge and much smaller than an atom. The particles were later renamed electrons. In 1912 he went on to develop mas spectrometry and in 1906 was awarded the Nobel Prize for Physics for research on conduction through gases.