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William Henry Yardley (1874-1936), founder of Princeps and Co
1936 Obituary 
WILLIAM HENRY YARDLEY founded in 1900 the firm of Princeps and Company, of Sheffield, and was concerned with the products manufactured under this name for the remainder of his career. The business is now carried on by Messrs. Roper and Wreaks, of Sheffield.
Mr. Yardley was born in 1874 and served his apprenticeship from 1888 to 1895 at the works of the Yorkshire Engine Company, Sheffield.
He afterwards became head draughtsman at Messrs. Steel, Peech and Tozer's steelworks; he designed large furnaces for steel manufacture by the Siemens process, and arranged for the conversion of a large proportion of the machinery to electric drive.
In 1899 he was appointed assistant engineer to Messrs. John Dewhurst and Son, Ltd., of Sheffield, and was responsible for the design of several types of quick-revolution engines and private electric power installations. He was so engaged until he founded the firm of Princeps and Company. His most successful inventions were various types of metallic packings, steam dryers and separators, air drainers for compressed air, and air filters for cleaning and drying air for cooling turbo-alternators, or for general air-conditioning in factories, cinemas, etc.
Although an invalid for the last two years of his life, he recently designed a self-cleaning all-steel air filter, the patent for which was granted only six months before his death, which occurred on 4th September 1936.
He had been an Associate Member of the Institution since 1901.