# Dictionary of National Biography, 1912 supplement/Petrie, William

​PETRIE, WILLIAM (1821–1908), electrician, born at King's Langley, Hertfordshire, on 21 Jan. 1821, was eldest of four sons of William Petrie (b. 1784), a war office official. His mother, Margaret, was daughter and co-heiress of Henry Mitton, banker, of the Chase, Enfield. In 1829 Petrie's father was sent to the Cape of Good Hope, where he acted until 1837 as deputy commissary-general, having as a near neighbour Sir John Herschel [q. v.], the astronomer. After home education in Cape Town, Petrie, with his brother Martin [q. v.], was entered at the South African College. He had early shown a liking for mechanics and chemistry, and his youthful studies were much influenced by Herschel's friendly encouragement. In 1836 Petrie commenced studying for the medical profession, attending the Cape Town Hospital, but in the year following the family returned to London, and the curriculum was not pursued. He then attended King's College. Later (1840) he studied at Frankfort-on-Main, devoting himself to magnetism and electricity. His inquiries bore fruit in 'Results of some Experiments in Electricity and Magnetism,' published in the 'Philosophical Magazine' in 1841; and 'On the Results of an Extensive Series of Magnetic Investigations, including most of the known Varieties of Steel,' communicated at the British Association's Southampton meeting of 1846 (see also papers presented to the Association in 1850).
Petrie returned to England in 1841, when he took out a patent for a magneto-electric machine. From 1846 to 1853 he worked assiduously at electric lighting problems in collaboration with William Edwards Staite. To Petrie's acumen is due the invention (1847–8) of the first truly self-regulating arc lamp. The essential feature was 'to impart more surely such motions to one of the electrodes that the light may be preserved from going out, be kept more uniform, and be renewed by the action of the apparatus itself whenever it has been put out.' Petrie's working drawings (still preserved) were made in conformity with this automatic principle, and he superintended the manufacture of the new lamp at Holtzapffel's works in Long Acre. It was submitted to rigorous tests, and was found to yield a light of between 600 and 700 standard candle-power, with a consumption of 1 lb. of zinc per 100 candle-power per hour. On 28 Nov. and 2 Dec. 1848 Petrie made displays with a lamp of 700 candle-power from the portico of the National Gallery, and on various nights in 1849 from the old Hungerford suspension bridge in London. The demonstrations were witnessed by Wheatstone and other prominent men of science. On 6 Feb. 1850, Petrie (with Staite) read a paper before the Society of Arts on 'Improvements in the Electric Light.' Petrie and Staite's long and courageous efforts to promote electric illumination were financially disastrous, and their pioneering services escaped the recognition of those who perfected the applications of the illuminant, Subsequently Petrie turned his attention to electro-chemistry, and superintended large chemical works; he introduced into the processes many improvements which he patented. He also designed and equipped chemical works in France, Australia, and the United States. For many years he was adviser and designer with Johnson, Matthey & Co.
Petrie died on 16 March 1908 at Bromley, Kent, and was buried there. He married on 2 Aug. 1851 , only child of Matthew Flinders [q. v.]. She was a competent linguist, and studied Egyptology. Under the pseudonym 'Philomathes' she published a work on the relation between mythology and scripture, and as 'X.Q.' contributed essays to periodical literature. Their son, the sole issue of the marriage, is William Matthew Flinders Petrie, F.R.S., professor of Egyptology in University College, London.
[Electrical Engineer, 29 Aug. 1902 and 6 Feb. 1903, articles by J. J. Fahie (portraits and diagrams); Roy. Soc. Catal. Sci. Papers; Patent Office Specifications; Illustrated London News, 9 Dec. 1848; private information.]
T. E. J.