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1931 Obituary 
IT is with great regret that we have to record the death of Captain Tolmie John Tresidder, C.M.G., late R.E., who for many years was a director of John Brown and Co., Ltd., and an authority on armour and projectiles.
Captain Tresidder died at his home in Upper Norwood on Friday last, March 20th, at the age of eighty-one. He was the elder son of the late Surgeon-General Tresidder, of H.M. Indian Medical Department, and was born at Chunar, India.
After completing his education at Dulwich and the Royal Military Academy, Woolwich, he joined the Royal Engineers, becoming Lieutenant in 1870 and Captain in 1882. He spent over ten years in Malta, where he carried out the drainage scheme of the five fortified cities, and was twice thanked by the Commander-in-Chief for his services. He retired from the Army in 1887.
His mathematical attainment, and aptitude for ballistics found use in his work with John Brown and Co., Ltd., where he devoted himself chiefly to the development of armour and armour-piercing projectiles.
In 1871, jointly with the late Mr. J. D. Ellis, he invented the system of chilled compound plates, combining the cementation and chilling processes in a manner which increased greatly the shot-resisting power of armour. This process was continued until 1896, when the firm's armour plants were adapted for the Krupp process.
Before he retired from active management in 1902, Captain Tresidder designed and supervised the installation of a complete new armour-making plant at the Atlas Steel Works of John Brown and Co., Ltd., Sheffield.
He continued to hold the office of a director of the company, to which he was appointed in 1894, until last year. He was also a director of the Anglo-French Nickel Company, Ltd., of Swansea.
In 1907 he read a. paper on "Modern Armour and its Attack before the Institution of Naval Architects, and he was awarded the Institution's Gold Medal the following year. He also received the Bessemer Gold Medal for original research.
Captain Tresidder was the author of many published works on armour and projectiles and the laws of high speed punching. Towards the end of the war he invented a special device for de-capping shells. It took the form of protective steel mats, and was fitted to a large number of battleships and cruisers. He was also the inventor of a slide rule for calculating the striking velocity of shell against armour, which found extended use. Even during the last two years his inventive faculty was not idle, and be patented two new types of micrometers for the internal and external fine gauging of parts.