Crookes tube
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A Crookes tube is an early experimental electrical discharge tube, with partial vacuum, invented by English physicist William Crookes and others around 1869-1875, in which cathode rays, streams of electrons, were discovered.
A Crookes tube: light and dark. Electrons (cathode rays) travel in straight lines from the cathode (left), as shown by the shadow cast by the metal Maltese cross on the fluorescence of the righthand glass wall of the tube. The anode is the electrode at the bottom.
Power off.
Without magnet, rays travel straight.
With magnet, rays are bent up.
William Crookes
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Sir William Crookes was a British chemist and physicist who attended the Royal College of Chemistry, now part of Imperial College London, and worked on spectroscopy. He was a pioneer of vacuum tubes, inventing the Crookes tube which was made in 1875. This was a foundational discovery that eventually changed the whole of chemistry and physics.
Sir William Crookes in 1906
Blue plaque, 7 Kensington Park Gardens, London
The element thallium, discovered by Crookes
The mineral crookesite, a selenide of copper, thallium and silver (Cu 7(Tl, Ag)Se 4), named for Crookes