Henry Bessemer obtains British patent no. 356 in the United Kingdom on February 12, 1856, and publicly presents his method — "The Manufacture of Malleable Iron and Steel without Fuel" — before the British Association for the Advancement of Science in Cheltenham on August 24 of the same year. The process consists of blowing air through molten iron to burn off excess carbon and other impurities by oxidation, also generating enough heat to keep the metal liquid with no need for additional fuel. It is the first cheap industrial method for mass steel production, and proves decisive for the expansion of railways, skyscrapers, and Industrial Revolution infrastructure. Exclusive attribution to Bessemer is a matter of historical dispute: the American engineer William Kelly, in Kentucky, had independently developed an essentially identical process from 1851 onward, but kept it secret and did not file for a patent until 1857 — after Bessemer's public announcement — which in practice nullified his temporal priority in terms of historical recognition, although the priority dispute was never fully resolved in the documentation of the time.