In this lecture I wish to give an account of some investigations which have led to the conclusion that the carriers of negative electricity are bodies, which I have called corpuscles, having a mass very much smaller than that of the atom of any known element, and are of the same character from whatever source the negative electricity may be derived. Nobel Lecture, Decemin Nobel Lectures: Physics, 1901-1921 (Amsterdam: Elsevier, 1967), pp. (See Pais 1986.) But Thomson did carry out this measurement and (later) the measurement of the particles's charge, and he recognized its importance as a constituent of ordinary matter. Thomson was not the only physicist to measure the charge-to-mass ratio of cathode rays in 1897, nor the first to announce his results. The credited discoverer makes crucial contributions to be sure, but often after fundamental observations have been made and tools invented by others. In what sense, then, can Thomson be said to have discovered the electron? After all, he did not invent the vacuum tube or discover cathode rays. Clearly, the characterization of cathode rays was a process begun long before Thomson's work, and several scientists made important contributions. The case of the electron raises several interesting points about the discovery process. He was awarded the Nobel Prize for physics in 1906 for this work, and in 1908 he was knighted. In 1899, he measured the charge of the particles, and speculated on how they were assembled into atoms. In 1897 he reported that "cathode rays" were actually negatively charged particles in motion he argued that the charged particles weighed much less than the lightest atom and were in fact constituents of atoms. For much of his career, Thomson worked on various aspects of the conduction of electricity through gases. Thomson was the Cavendish professor of Experimental Physics at Cambridge University and director of its Cavendish Laboratory from 1884 until 1919.
Thomson, 1856-1940 see photo at American Institute of Physics) is widely recognized as the discoverer of the electron.
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