While apparently not the originator of the process, Bessemer is without any doubt entitled to most of the credit he received. There is no proof that he had heard of Kelly’s experiments when he began his own or that he was aided by Kelly’s discoveries. He worked out the details of the process independently, as had Kelly, and it was Bessemer who put it on a commercial basis. As has occurred with other new processes Bessemer’s first licensees were not particularly successful. When those who had bought the right to use his process had failed in their efforts to use it, and become discouraged as most of them did, he quietly bought back their rights and went ahead with his development of the process. Perhaps no man ever exhibited more perseverance in continuing experiments and development under very discouraging conditions than did Henry Bessemer. He had faith. [Illustration: SECTIONAL VIEW OF A MODERN CONVERTER SHOWING AIR DUCT AND TUYÈRES ] He had a genius for invention and was thorough in his experimental work. Practically no type of converter has since been brought out that he did not think of and try, and the process has been modified in but one or two important particulars in the years that have passed. The essential part of the Bessemer process is the blowing of air through molten cast iron to remove the metalloids by which cast iron differs from steel and wrought iron, as has been explained before. This being the essential point, and at first thought the lack of fuel seeming so peculiar, we must describe what happens during the Bessemer “blow.” [Illustration: POURING CHARGE OF MOLTEN PIG IRON INTO CONVERTER ] Technically speaking, the metalloids are “oxidized.” Oxidation is the chemical uniting of oxygen, generally from the air, which has 21 per cent of this element, with another element or material such as iron, silicon, carbon, wood, coal, etc. If the oxidation is slow as in the “rusting” of iron, the resulting heat dissipates as fast as it is generated and the change is hardly noticeable. If, however, the reaction occurs rapidly and with vigor enough, we say that the material “burns.” The latter sort of oxidation is what we call “combustion.” The affinity between the metalloids and oxygen has been noted by us before, but in those cases most of the oxygen came from a different source. In the wrought iron process most of it was furnished by the iron ore or scale which was stirred into the metal, or by the slag which covered the “bath.” In the Bessemer, or as it was first known in America, “Kelly’s air blowing process,” the oxygen of the air blown through the molten metal directly oxidizes or burns out the carbon, silicon, and manganese. The extremely rapid oxidation of these furnishes the heat. The iron, then, furnishes its own fuel and _no outside combustible is needed_. How can this be?