Page:Dictionary of National Biography, Third Supplement.djvu/162

 CROMER, first (1841-1917), statesman. [See .]  CROOKES, WILLIAM (1832-1919), man of science, was born in London 17 June 1832, the eldest son of Joseph Crookes, a tailor of north-country origin, by his second wife, Mary Scott. He received some instruction at a grammar school at Chippenham, but his scientific career began when, at the age of fifteen, he entered the Royal College of Chemistry in Hanover Square, London, under August Wilhelm von Hofmann. From 1850 to 1854 he filled the position of assistant in the college, and soon embarked upon original work, not indeed in the region of organic chemistry whither the inspiration of his distinguished teacher might have been expected to lead him, but on certain new compounds of the element selenium, the selenocyanides. These form the subject of his first published papers (1851). Leaving the Royal College, he became in 1854 superintendent of the meteorological department at the Radcliffe Observatory in Oxford, and in 1855 was appointed lecturer in chemistry at the Chester training college. In 1856 he married Ellen, daughter of William Humphrey, of Darlington, by whom he had three sons and a daughter. From this time his life was passed in London, and devoted mainly to independent work, journalistic, consulting, and academic. In 1859 he founded the Chemical News, which he edited for many years and conducted on much less formal lines than is usual with journals of scientific societies. After 1880 he lived at 7 Kensington Park Gardens, where in his private laboratory all his later work was carried out.

Crookes’s life was one of unbroken scientific activity. He was never one of those who gain influence by popular exposition; neither was he esoteric. The breadth of his interests, ranging over pure and applied science, economic and practical problems, and psychical research, made him a well-known personality, and he received many public and academic honours. He was knighted in 1897, and in 1910 received the order of merit. At various times he was president of the Chemical Society, the Institution of Electrical Engineers, the Society of Chemical Industry, the British Association, and, from 1913 to 1915, of the Royal Society. He died in London 4 April 1919, two years after his wife, to whom he had been, much devoted.

The work of Crookes extended over the regions of both chemistry and physics. Its salient characteristic was the originality of conception of his experiments, and the skill of their execution. It is probably just to say that his theoretical speculations, imaginative and stimulating as they may have been, were of less permanent importance. He was always more effective in experiment than in interpretation. His first great discovery was that of the element thallium, announced in 1861. By this work his reputation became firmly established, and he was elected a fellow of the Royal Society in 1863. The method of spectrum analysis, introduced by Bunsen and Kirchhoff, was received by Crookes with great enthusiasm, and, on applying it to the examination of the seleniferous deposit from a sulphuric acid factory, he discovered an unknown green line in the spectrum. The isolation of the new metallic element, thallium, followed, and the investigation of the properties of its compounds, which are of great chemical interest. Finally, in 1878, he determined the atomic weight of the new element in a research which is still a model of analytical precision.

Two main lines of research now occupied the attention of Crookes for many years. These were the properties of highly rarefied gases, with which he began to occupy himself immediately, and the investigation of the elements of the ‘rare earths’, upon which he embarked shortly after 1880. His attention had been attracted to the first problem in using a vacuum balance in the course of the thallium researches. He soon discovered the phenomenon upon which depends the action of the well-known little instrument, the Crookes radiometer, in which a system of vanes, each blackened on one side and polished on the other, is set in rotation when exposed to radiant energy. He did not, however, provide the true explanation of this apparent ‘attraction and repulsion resulting from radiation’. Of more fundamental importance were his researches on the passage of the electrical discharge through rarefied gases. He found that as the attenuation of the gas was made greater the dark space round the negative electrode extended, while rays, now known as cathode rays, proceed from the electrode. He investigated the properties of the rays, showing that they travel in straight lines, cause phosphorescence in objects upon which they impinge, and by their impact produce great heat. He believed that he had discovered a fourth state of matter, which he called ‘radiant matter’. But his theoretical  136