Page:Popular Science Monthly Volume 39.djvu/761

Rh much of it for remelting in pots, and a great deal being used for forgings. In the "Centennial Exhibition of 1876" there was shown in the Swedish department by the "Motala Iron and Steel Works" a number of welded coils of "puddled steel" intended for "gun-hoops" and several finished "hoops."

The introduction of the "Bessemer process" into the United States preceded by a few years that of the "open-hearth," but their advent was practically coincident. For convenience, the latter will be described first. By this process pig iron of a suitable quality is melted on the hearth of a reverberatory furnace, and then either wrought-iron "scrap" or iron ore is mixed therewith.

The principle of the "open-hearth" process was well understood by metallurgists for many years before it could be carried into practice, owing to the impossibility of securing a sufficiently intense and continuous heat in any ordinary form of reverberatory furnace. As early as 1824, M. Bréant stated that "it would be possible to produce cast steel on a very large scale in reverberatory furnaces by following a process analogous to that of the depuration of bell-metal—that is to say, by adding to the metal in fusion [pig iron] a portion of the same metal oxidized, or, still better, natural oxide of iron." In 1845 Josiah Marshal Heath (who invented the use of manganese in melting steel in pots) patented a method of making steel in large quantities by melting cast and wrought iron together upon the open hearth of a reverberatory furnace; and, for the purpose of preventing the contamination of the metal by the ashes of solid fuel, he designed to heat his furnace by jets of gas. But the experiments of Heath, although pointing out clearly the road to success, were not themselves successful. M. Alfred Sudre patented in England, December 31, 1858, a method of melting steel in a reverberatory furnace. He made experiments in 1860 and 1861 near Paris, the expense of which was defrayed by the Emperor of the French, but they fell short of a commercial success. It was not until 1864—forty years after the original suggestion of M. Bréant—that the making of steel by the fusion of pig iron and wrought-iron "scrap" on the open hearth of a gas-fired reverberatory furnace could be regarded as commercially and technically successful. This result was attained by a combination of the "regenerative gas furnace," then recently invented, with the perseverance and technical skill of Messrs. Émile and Pierre Martin, who, notwithstanding its failure in other places, erected one of the Siemens furnaces in their works at Sireuil, France. Evidently there was a lurking doubt in the minds of the Messrs. Martin, for this furnace seems to have been so constructed that, if it failed as a melting, it would succeed as a