Text: Same as RADIOMETER. CROOKES, SIR WILLIAM (1832-1919) ‹English chemist and physicist. Born in London June 17th, 1832, Crookes was educated at the Royal College of Chemistry and afterwards became assistant in the meteorological department of the Radcliffe Observatory, Oxford. In 1855 he obtained a chemical post at Chester. Crookes early began that series of brilliant researches which has left its mark on the scientific progress of the nineteenth century. In 1861 he isolated the new element thallium, during the investigation of the atomic weight of which he made the discovery of his radiometer. This led to his researches on the phenomena of electric discharges through highly exhausted tubes, or Crookes tubes. The illustration shows such a tube. When a current is passed through it, cathode narticles travel along it. His discoveries on these phenomena led directly to the development by Sir J. J. Thomson of the now generally accepted electron theory. (q.v.) In 1883 he began his study of the rare earths, and in 1892 he forecast Radio telegraphy on the strength of Lodge's and Hughes' experiments. Knighted in 1897, Crookes was awarded the Royal medal in 1875, the Davy medal in 1880, and the Copley medal of the Royal Society in 1904 and the O.M., in 1910. He died in London. ADril 4th. 1919.

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