The process consists in forcing through molten cast iron, held in a vessel called a converter, a stream of cold air under pressure. The combination of the oxygen in the air with the silicon and carbon in the metal raises the temperature of the latter in a spectacular way and after "blowing" for a certain period, eliminates the carbon from the metal. Since steel of various qualities demands the inclusion of from 0.15 to 1.70 percent of carbon, the blow has to be terminated before the elimination of the whole carbon content; or if the carbon content has been eliminated the appropriate percentage of carbon has to be put back. This latter operation is carried out by adding a precise quantity of manganiferous pig-iron (spiegeleisen) or ferromanganese, the manganese serving to remove the oxygen, which has combined with the iron during the blow. The controversy which surrounded its development concerned two aspects of the process: The use of the cold air blast to raise the temperature of the molten metal, and the application of manganese to overcome the problem of control of the carbon and oxygen content. Bessemer, who began his experiments in the making of iron and steel in 1854, secured his first patent in Great Britain in January 1855, and was persuaded to present information about his discovery to a meeting of the British Association for the Advancement of Science held at Cheltenham, Gloucestershire, in August 1856. His title "The Manufacture of Iron without Fuel" was given wide publicity in Great Britain and in the United States. Among those who wrote to the papers to contest Bessemer's theories were several claimants to priority of invention. Two men claimed that they had anticipated Bessemer in the invention of a method of treating molten metal with air-blasts for the purpose of "purifying" or decarbonizing iron. Both were Americans. Joseph Gilbert Martien, of Newark, New Jersey, who at the time of Bessemer's address was working at the plant of the Ebbw Vale Iron Works, in South Wales, secured a provisional patent a few days before Bessemer obtained one of his series of patents for making cast steel, a circumstance which provided ammunition for those who wished to dispute Bessemer's somewhat spectacular claims. William Kelly, an ironmaster of Eddyville, Kentucky, brought into action by an American report of Bessemer's British Association paper, opposed the granting of a United States patent to Bessemer and substantiated, to the satisfaction of the Commissioner of Patents, his claim to priority in the "air boiling" process.