146 BULLETIN 12, UNITED STATES NATIONAL MUSEUM. 



A Be.ssemer works geiuniilly coiitaiiKs :i pair of converters, iuul iti the 

 best works about tliirty blows arc made during; tlie li4 hours. 



This process requires certain characteristics in the pig-iron to be 

 used. In general it should contain about 2 per cent, of sdicon in order 

 to give the necessary heat, by its combustion, to the bath of metal to 

 keep it fluid. It should contain from 3 to 5 i)er cent, of carbon, and 

 about 1 i)er cent, of manganese is desirable. Since all the phosphorus 

 and sul[>hur present in the pig-iron is found in the steel, and since they 

 injure the quality of the metal, it is absolutely necessary that they 

 should be kept very low in the pig, one-tenth of 1 per cent, being the 

 limit for phosphorus, while the sulphur is generally kept below half that 

 amount. 



The converter lining, especially on the bottom, requires frequent re- 

 pairs, since it is subject to high temperature, to violent mechanical mo- 

 tion, and to destructive chemical action. The bottom is therefore made 

 separate, and has to be removed on the average after from eight to 

 ten blows, while from three to four sets of tuyeres are burned out every 

 24 hours. For this reason much more time is taken up in the rei)airs 

 than in the actual [)rocess of conversion. 



The pig-iron is sometimes melted in auxiliary cupola furnaces, while 

 at others it is taken direct from the blast furnace to the converter. The 

 Spiegel is melted in a cupola, tapped out into a ladle, and weighed, so 

 as to introduce the exact amount required. 



The casting ladle is huug on an hydraulic crane, which swings around 

 in a circle over the molds in which the ingots are cast. 



The Bessemer process is eminently fitted for the production of large 

 amounts of steel at a very low cost. Formerly its use was almost 

 entirely limited to the manufacture of steel rails, but it is now being 

 used largely for other i>urposes. 



The construction of the converter is shown in pl. xv, and the general 

 arrangement of the steel house in pl. xvr. 



THE SOUTH CHlfAGO IJKSSKM I'.H WUJtKS. 



These works are situated lii miles from (Chicago, on the nortli side of 

 Calumet River, at its mouth. They have a frontage of 2,.500 feet on the 

 lake, 2,400 feet on the Calumet River, and a slip for vessels 1,000 feet 

 long. There are also 11 miles of railroad track for the handling of 

 material, and connecting the works with six trunk lines of railroad. 

 Thus they have most ample means for getting supplies and shipping 

 ])roduct. They cover. 85 acres. The plant comprises four blast furnaces, 

 three 10-ton converters, and .1 rail mill where the ingots can be rolled 

 in a single heat. Each department is thoroughly e(piii)ped with the 

 7nost modern unu^hinery. 



The ores smelted in the blast furnaces are obtained mostly fiom the 

 Lake Superior regions, and frequently' as many as twelve different 

 varieties are used in a single charge. This mixture is made up in 



