Page:Dictionary of National Biography, Third Supplement.djvu/28

 photographic image, and his introduction in 1880 of a new developing agent, hydroquinone.

But Abney's most notable experimental work related to spectro-photography, colour analysis, and colour vision. He re-drew the three-colour sensation curves associated with the Young-Helmholtz theory of colour vision, and as early as 1880 succeeded in making photographic plates sensitive to the red and infra-red; with these he mapped this region of the solar spectrum with an accuracy comparable to that of the standard maps of the normal solar spectrum prepared by A. J. Ångstrom and H. A. Rowland. He made thousands of these specially sensitive plates for use in his chemical and astronomical investigations.

Abney was awarded in 1882 the Rumford medal of the Royal Society, of which he had been elected a fellow in 1876. He was made a C.B. in 1888, and K.C.B. in 1900. He was president of the Royal Photographic Society from 1892 to 1894, in 1896, 1903, and 1905; of the Royal Astronomical Society, 1893–1895; and of the Physical Society, 1895–1897. In the autumn of 1920 he went to Folkestone because of his failing health, and died there on 3 December.

Abney married twice: first, in 1864 Agnes Mathilda (who died in 1888), daughter of Edward W. Smith, of Tickton Hall, Yorkshire, by whom he had one son and two daughters; secondly, in 1890 Mary Louisa, daughter of the Rev. E. N. Meade, D.D., of St. Mary's Knoll, Scarborough-on-Hudson, U.S.A., by whom he had one daughter.

The diversity of Abney's scientific labours makes it difficult to give an adequate review of them. Over one hundred of his papers are recorded in the Royal Society's Catalogue and as many more are to be found in the Photographic Journal and kindred publications. His experimental work lacked nothing for completeness and precision, yet he had little liking for meticulous refinement in research, and his methods were remarkable for their ingenious simplicity. He underrated the advances made (1891) in sensitometry by F. Hurter and V. C. Driffield, yet his Instruction in Photography (1870) and his Treatise on Photography (1875), in their latest editions, still rank among the most valuable photographic textbooks in the English language. His investigations of the problems of colour vision he summarized in his Trichromatic Theory of Colour (1914). He was a keen traveller, and wrote an account of Thebes, and its Five Great Temples (1876) and was joint author, with C. D. Cunningham, of The Pioneers of the Alps (1888).

 ALCOCK, JOHN WILLIAM (1892–1919), airman, was born at Manchester 6 November 1892, the eldest child and eldest son of John Alcock, horsedealer, by his wife, Mary Whitelegg, both of that city. He was educated at the parish school, St. Anne's-on-Sea, and entered the Empress motor works in Manchester as an apprentice in 1909. Flying soon attracted him, and in 1910 he went to Brooklands, where, as mechanic to the French pilot Maurice Ducrocq, he learned the art of ‘tuning’ an aeroplane. Alcock took his aviator's certificate in November 1912, and was then employed by the Sunbeam motor-car company as a racing pilot.

In November 1914 Alcock joined the Royal Naval Air Service as a warrant-officer instructor, serving mostly at the Royal Naval Flying School at Eastchurch, Kent. He received his commission as flight sub-lieutenant in December 1915, but was retained at Eastchurch until December 1916, when he was posted to No. 2 wing in the Eastern Mediterranean. From his base at Mudros he took part in many long-distance bombing raids. On 30 September 1917, flying a single-seater Sopwith ‘camel’, he earned the distinguished service cross for a gallant and skilful attack on three enemy seaplanes, two of which crashed into the sea. At 8.15 p.m. on the same day, Alcock left on a Handley Page aeroplane to bomb Constantinople. He was over the Gallipoli peninsula when the failure of one of his two engines compelled him to turn back. He covered sixty miles with one engine, but was then forced to alight in the sea, near Suvla Bay. Alcock and his crew of two were afloat on their craft for two hours, but their Verey lights failed to attract the attention of the British destroyers, and as the aeroplane now began to sink, they left it and struck out for the land. They got ashore after an hour in the water, and lay concealed throughout the night, but at noon were made prisoners by the Turks.

Alcock was released and returned to England after the armistice, and he left the Royal Air Force in March 1919 with