Several years since, a pneumatic process of manufacturing wrought iron was invented and patented by Dr. Chapin, and an experimental plant was erected near Chicago.  Enough was done to demonstrate, first, that an iron of unprecedentedly good qualities was attainable from common pig; and second, that the cost of its manufacture would not exceed that of Bessemer steel.  Nevertheless, owing to lack of funds properly to push the invention against the jealous opposition which it encountered, the enterprise came to a halt until quite recently, when its merits found a champion in Gustav Lindenthal, C.E., member of this club, who is now the general manager of the Chapin Pneumatic Iron Co., and under whose direction this new quality of iron will soon be put upon the market.

The process of manufacture is briefly as follows:  The pig metal, after being melted in a cupola and tapped into a discharging ladle, is delivered into a Bessemer converter, in which the metal is largely relieved of its silicon, sulphur, carbon, etc., by the ordinary pneumatic process.  At the end of the blow the converter is turned down and its contents discharged into a traveling ladle, and quickly delivered to machines called ballers, which are rotary reverberatory furnaces, each revolving on a horizontal axis.  In the baller the iron is very soon made into a ball without manual aid.  It is then lifted out by means of a suspended fork and carried to a Winslow squeezer, where the ball is reduced to a roll twelve inches in diameter.  Thence it is taken to a furnace for a wash heat, and finally to the muck train.

No reagents are employed, as in steel making or ordinary iron puddling.  The high heat of the metal is sufficient to preserve its fluidity during its transit from the converter to the baller; and the cinder from the blow is kept in the ladle.

The baller is a bulging cylinder having hollow trunnions through which the flame passes.  The cylinder is lined with fire brick, and this in turn is covered with a suitable refractory iron ore, from eight to ten inches thick, grouted with pulverized iron ore, forming a bottom, as in the common puddling furnace.  The phosphorus of the iron, which cannot be eliminated in the intense heat of the converter, is, however, reduced to a minimum in the baller at a much lower temperature and on the basic lining.  The process wastes the lining very slightly indeed.  As many as sixty heats have been taken off in succession without giving the lining any attention.  The absence of any reagent leaves the iron simply pure and homogeneous to a degree never realized in muck bars made by the old puddling process.  Thus the expense of a reheating and rerolling to refine the iron is obviated.  It was such iron as here results that Bessemer, in his early experiments, was seeking to obtain when he was diverted from his purpose by his splendid discoveries in the art of making steel.  So effective is the new process, that even from the poorest grades of pig may be obtained economically an iron equal in quality to the refined irons made from the best pig by the ordinary process of puddling.