The fearsome Fomorian

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In his investigations of the conduction of electricity in low-pressure gases, he found that as the pressure was reduced, the negative electrode (cathode) appeared to emit rays (so-called "cathode rays", now known to be a stream of free electrons, and used in cathode ray display devices). As these examples indicate, he was a pioneer in the construction and use of vacuum tubes for the study of physical phenomena. As a consequence, he was one of the first scientists to investigate what is now called plasma, identifying it as the fourth state of matter in 1879. He also devised one of the first instruments for studying nuclear radioactivity, the spinthariscope.

Portrait of William Crookes, age 18

Portrait of William Crookes, age 24

Portrait of William Crookes, age 57

Portrait of Sir William italy email list Crookes, OM, aged 79



Sir William Crookes by Sir Leslie Ward, 1902

Crookes investigated the properties of cathode rays, showing that they travel in straight lines, cause fluorescence when they fall on some substances, and that their impact can produce great heat. He believed that he had discovered a fourth state of matter, which he called 'radiant matter', but his theoretical views on the nature of 'radiant matter' were to be superseded. He believed that the rays consisted of streams of particles of ordinary molecular magnitude. It was left to Sir J. J. Thomson to expose the subatomic nature of cathode rays (consisting of streams of negative electrons). However, Crookes' experimental work in this field was the basis of discoveries which eventually changed the whole of chemistry and physics.