Sydney E.T. Ewing, consulting engineer, was a member of the (British) Institution of Electrical Engineers but by 1904 he resided in Johannesburg. He contributed a paper on "Some practical aspects of electric winding" to the Transactions of the South African Institute of Electrical Engineers (1911/12, Vol. 3, p. 119) which earned him the institute's annual gold medal award. A subsequent paper by him (ibid, 1916, Vol. 7(12), p. 318) dealt with a "Comparison of Ward-Leonard and three-phase winding".
In later years Ewing became involved also in other aspects of engineering and distinguished himself particularly as an inventor. For example, with J.L. Willey he registered a patent for improved methods of ore reduction (1923) and published a paper (by C.R. Davis, Willey and Ewing) on "Recent developments in the fine grinding and treatment of Witwatersrand ores" (Transactions of the American Institute of Mining and Metallurgical Engineers, 1924). With two others he next obtained patents for a method of electric heating (1928) and for electrically heating the ends of rock drills (1928). He and A.L. Egan registered a patent in 1933 for a retarding device for machinery. After publishing a treatise entitled Mine cooling by devaporised compressed air (1934, with A.L. Egan) the two authors registered a United States patent (1937) for methods and apparatus to produce de-humidified compressed air to be used especially to condition the atmosphere in mines. With J.L. Willey he also registered a patent for a method and apparatus to separate solid particles (1935).
In 1904 Ewing became a member of the South African Association for the Advancement of Science. He was married to Emily Jane, born Holter, with whom he had four sons and a daughter, but they were divorced in 1909. Later he married (in Johannesburg) Maud Rees Pryce, born Watson, with whom he had a son. In 1938, presumably after his retirement, he bought a plot on the west bank of the Buffalo River from the municipality of East London. However, he died in Johannesburg.