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More than 5000 entries on the history, culture and life of Britain (published in 1993 by Macmillan, now out of print)
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William Crookes
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(1832–1919, kt 1897) Chemist and physicist who in 1861 discovered the element thallium by observing a green line in the spectrum of selenium (the element was first isolated in France the following year, by Claude-Auguste Lamy). He invented the radiometer known by his name, in which lightweight vanes blackened on one side revolve in a near-vacuum when light or other radiant energy falls upon them. In his later years he did much work on cathode rays, and predicted the need for nitrogen fertilizers to meet the demands of increasing populations.
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