This machine enlarged at one bound the whole scale of working in iron, and permitted Maudsley's lathe to develop its entire range of capacity. The old 'tilt-hammer' was so constructed that the more voluminous the material submitted to it, the _less_ was the power attainable; so that as soon as certain dimensions had been exceeded, the hammer became utterly useless. When the _Great Western_ steamship was in course of construction, tenders were invited from the leading mechanical firms for the supply of the enormous paddle-shaft required for her engines. But a forging of the size in question had never been executed, and no firm in England would undertake the contract. In this dilemma, Mr Nasmyth was applied to, and the result of his study of the problem was this marvellous steam-hammer--so powerful that it will forge an Armstrong hundred-pounder as easily as a farrier forges a horse-shoe, and so delicately manageable that it will crack a nut without bruising its kernel!
In 1722, Réaumur produced steel by melting three parts of cast-iron with one part of wrought iron (probably in a crucible) in a common forge; he, however, failed to produce steel in this manner on a working scale. This process has many points in common with the Indian Wootz-steel manufacture.
As we have seen, to Benjamin Huntsman, a Doncaster artisan, belongs the credit of first producing cast-steel upon a working scale, as he was the first to accomplish the entire fusion of converted bar-iron (that is, blister-steel) of the required degree of hardness, in crucibles or clay pots, placed among the coke of an air-furnace. This process is still carried on at Sheffield and elsewhere, and is what is generally known as the crucible or pot-steel process. It was mainly supplementary to the cementation process, as formerly blister-steel was alone melted in the crucibles; but latterly, and at the present time, the crucible mode of manufacture embraces the fusion of other varieties and combinations of metal, producing accordingly different classes and qualities of steel.
In 1839, Josiah Marshall Heath patented the important application of carburet of manganese to steel in the crucible, which application imparted to the resulting product the properties of varying temper and increased forgeability. He subsequently found out that a separate operation was not necessary to form the carburet--which is produced by heating peroxide of manganese and carbon to a high temperature--but that the same result could be attained by simply in the first instance adding the carbon and oxide of manganese direct to the metal in the crucible. He unsuspectingly communicated this after-discovery to his agent--by name Unwin--who took advantage of the fact that it was not incorporated in the wording of the patent, and so was unprotected, to make use of it for his own advantage. The result was one of the most remarkable patent trials on record, extending over twelve years, and terminating in 1855 against the patentee--a remarkable instance of the triumph of legal technicalities over the moral sense of right.