Metallurgist and inventor; educated Dulwich College. Schoolmaster. Clerk at police courts. Studied metallurgy and experimented. Discovered (1875) a method for eliminating phosphorous from pig-iron (a major impurity in some iron ores) in the Bessemer converter. He devised a process in 1876-1877 with his cousin Percy (Carlyle) Gilchrist (1851-1935) for manufacturing low -phosphorous steel. The method is now called the Thomas-Gilchrist process, the Thomas process or the Basic process. Secured a large fortune from his patents. Visited United States, 1881. Travelled abroad for his health.