Sir William Crookes

Library of Congress

[b. London, June 17, 1832, d. London, April 4, 1919]

William Crookes trained as a chemist but became interested in spectrometry and electrical discharges into near vacuums; his major discoveries emerged from these interests. In 1861 he recognized that a green line on a spectrogram must be a new element; he isolated the element and named it thallium. In 1875 he invented the radiometer, an evacuated transparent bulb that has an arrangement of vanes, black on one side and silvered on the other, that spins when placed in a light (the cause is unequal heating of the gases left in the bulb near the black and the silver vanes). Crookes's name is preserved in his vacuum tubes. He did not invent the vacuum tube with a cathode and anode to produce an electric current, but his Crookes tubes were superior. With them he discovered the basic properties of the electric discharge, or cathode ray, from which J.J. Thomson was to discover the electron, confirming Crookes's own views on the nature of cathode rays.

History of Science and Technology, edited by Bryan Bunch and Alexander Hellemans. Copyright © 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.