Stoney, George Gerald (1863–1942), engineer and pioneer of steam turbine engines, was born 28 November 1863 in Dublin, eldest son of George Johnstone Stoney (qv), scientist and secretary of QUI (1857–79), and his wife Margaret, only daughter of Robert Johnstone Stoney of Parsonstown (Birr), King's Co. (Offaly). His sister was Florence Ada Stoney (qv), OBE, a pioneer in the field of radiology. While George Gerald was still a young child, his father was appointed by William Parsons (qv), 3rd earl of Rosse, as tutor to Charles (later Sir Charles) Parsons (qv) and his brothers, marking the beginning of a lifelong connection between the two men.
He entered TCD in June 1882 and graduated as second senior moderator and gold medallist in experimental science in 1886. He subsequently graduated with a degree in engineering (1887), before going to work in the office of his uncle, Bindon Blood Stoney (qv), chief engineer of the Dublin port and docks board. In September 1888 he joined the staff of Clarke, Chapman & Co., an engineering firm based at Gateshead, which Charles Parsons had joined in 1884 as a junior partner and chief electrical engineer. It was here that he first collaborated with Parsons in the development of the steam turbine engine, initially working on small turbines designed to supply the electricity for ships' lighting systems. In 1889 he moved with Parsons to his new engineering firm at Heaton, C. A. Parsons & Co., where he worked as a fitter before being made foreman of the test house. He continued to collaborate with Parsons in the development of the reaction steam turbine, and in 1894 he supervised the fitting-out of their famous test-ship, the Turbinia. Appointed as chief designer of the steam turbine department in 1895, he was one of the crew of the Turbinia when she joined the fleet, uninvited, at the diamond jubilee review at Spithead in 1897. Although admiralty chiefs were somewhat annoyed at this unofficial intrusion, they were impressed with Turbinia's speed of over 30 knots, ensuring government support for the further development of Parsons's turbine technology.
In 1910 Stoney was appointed technical manager of the Heaton works, a position that involved increased management responsibilities alongside his technical duties. Elected FRS in 1911, he began to have differences with Parsons about how the Heaton works were being managed. Parsons seemed content to run the company as an experimental works, allowing other companies to develop his turbines under licence, while Stoney wished to organise on more commercial lines. In June 1912 matters came to a head and, in ‘a moment of extreme vexation’ (Scaife, 444), he resigned. He initially worked as a consulting engineer and in 1914 became the secretary of the Tyneside Irish Committee and helped organise volunteer battalions for the war effort. During the first world war he worked on admiralty research projects, including the anti-submarine scientific research committee. In 1915 he was appointed as a member of the Newcastle upon Tyne education committee before accepting the chair of mechanical engineering at the College of Technology and Victoria University, Manchester (1917–26).
Reconciled with Parsons in 1926, he resigned his professorship and returned to the Heaton works, where he was appointed as director of research. He published numerous papers on general engineering subjects and also the development of the steam turbine. These appeared in journals such as Proceedings of the Royal Society, Proceedings of the Royal Dublin Society, Engineering, and the Journal of the Institute of Electrical Engineers. He also wrote a series of memoirs of his time at Parsons & Co., which were published in the Heaton Works Journal. In 1920 he was awarded an honorary doctorate by Durham University. Other honours included the Watt Medal of the Institute of Civil Engineers (1906) and the Parsons Memorial Medal of the Institute of Electrical Engineers (1937). He retired in 1930 and died at Newcastle upon Tyne on 15 May 1942.
He married (1894) Isabella Mary (d. 1930), second daughter of Michael Lowes of Corbridge on Tyne; they had no children. A portrait of him, by T. B. Garvie, was later placed in the Heaton works. There is a collection of his letters in the Parsons collection of the Science Museum in London.