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iron, since if all the carbon were blown out of evenhematite English iron, the remaining metal washighly red-short. Swedish pig iron contained lesssilicon than English hematite, while it containedalso from 2 to 4 per cent, of manganese. Hence itrequired less blowing, and when the operation wasfinished there still remained some manganese tocounteract the excess of oxygen required; and thesofter products when made from Swedish iron werethus found to work well.
The effect of manganese upon steel was prettywell known at the time of Bessemer’s invention, inconsequence of the discoveries of Heath; but theidea of applying the manganese in the form of ametallic alloy is due to Robert Mushet. He patented(September 22, 1856) the addition of molten Spie-geleisen to the decarburized Bessemer metal, forthe double purpose of restoring a fixed quantity ofcarbon and adding manganese to the product, andit was this addition to Bessemer’s invention thatmade it perfect; and Musiiet’s plan of completelydecarburizing the metal, and then adding a knownquantity of carbon, is now almost invariably followed.Unfortunately for Mushet, his patent right wasallowed to lapse through the non-payment of thethird year’s duty, and his invention became publicproperty. This seems, no doubt, a great injusticeto Mushet, but through the influence of Dr. Percyhis claims received recognition from Bessemer.
Although little notice was taken of Bessemer’spaper to the Institution of Civil Engineers , or of theremarkable specimens then shown, yet the processgradually made its way; and the success of theworks which he and his partner erected at Sheffield(and in the management of which Mr. Bessemerenlisted the quiet talent of his brother-in-law, Mr.Allen), soon induced other Sheffield manufacturersto take it up; and first John Brown & Co., andthen others, discovered that the manufacture ofBessemer steel was a profitable operation, as wellas a wonderful metallurgical success.
The convertor used in the first instance byBessemer, and then introduced into Sweden , whereit has been constantly employed up to the presenttime, was a fixed vertical cylinder, lined with re-fractory material, and having horizontal twyers atthe bottom, with a separate tap-hole. This wasfirst thoroughly heated by fuel, the blast was puton, and then from 1 to 2 tons of molten pig run in.Refining commenced at once with an outburst ofsparks, and frequent ejection of slag and somemetal, the flame gradually increasing to dazzlingwhiteness. When the metal was assumed to besufficiently decarburized, it was tapped into a ladle,and cast into ingots. After the invention by Bes-semer of the movable convertor, the power ofproduction was so greatly increased, that it becamenecessary to design an apparatus for dealing withlarge quantities of fluid metal, and removing themoulds and ingots with facility; and on January 8,1862, Bessemer took out a patent for the employ-ment of a pair of converting vessels, with a centre-casting ladle between them—the whole being moved
by hydraulic power, and forming such an extremelypractical and efficient set of apparatus for carryingon the process, that although very many clerver menhave since done their best to improve upon theseplans, the essential portions are retained in the mostapproved plants of the present day. In 1863 theplan of having duplicate bottoms removable fromthe vessel, so that they could be got ready before-hand, was introduced, but it did not find generalfavour for many years; and the improvement ofthis portion, by so arranging the parts that thejoint between the old lining and the new bottomcould be made from the outside, was due to A. L.Holley, of the United States , who took out hisEnglish patent in 1870. Holley’s plan of replacingthe bottom and the lengthening of the vessels, soas to prevent the metal and slag being blown out,which was first introduced by Pink of Iloerde, areprobably the greatest improvements that have beenmade in the Bessemer apparatus. Plate II. shows thearrangement of Bessemer plant of the most approvedEnglish fashion; and Plates III. and IV. show theelevation and plan of one of the most recent arrange-ments, as designed by Holley for American works.The reader will thus be able to see the points ofdifference in the practice of the two countries—a a are cupolas for melting pig iron; a', spiegelcupolas; b, receiving ladle; c, runners for moltenmetal; d, convertors; e, the steel casting ladle;,/? centrecrane; g g, ingot cranes; k, ingot moulds. The English plan is mainly followed on the Continent. It willbe observed that an essential point of difference liesin the arrangement of the convertors. In the Eng-lish plan, as designed by Bessemer, they are placedface to face, and only little more than half thecircle traced by the casting ladle can be used forplacing moulds. In the American system the twovessels are placed side by side, and thus leave aboutfour-fifths of the circle available for moulds. Thisso facilitated the work of casting and removing theingots, &c., that a considerably greater number ofcasts could be dealt with in a given time; and thuswhile in English practice 350 tons of ingots perweek was considered a good output from a pairof vessels, the Americans were getting 500 or more.But this large output was only rendered possible byincreased facilities at other points, and of these Hol-ley’S “ dry bottom,” as it has been termed, and the useof an intermediate receiving ladle for collecting andweighing the metal from the cupolas and holding itready for the convertors, are two of the most important.
In the earlier practice it was deemed necessaryto remelt the pig iron in reverberatory furnaces,on the ground, that if melted in a cupola, theiron would become deteriorated. This continuedto be the practice for a long time, entailing greatwaste of fuel (as it required from 9 to 10 cwts.of best coal to melt 1 ton of iron), and also ofthe iron itself. It is somewhat doubtful who firstproved that this expensive melting was unnecessary;the merit of having first used iron melted in a cupolabeing claimed both by the late George Brown, ofSir J. Brown & Co., and also by John Birch, of the