IKON, COBALT, AND NICKEL 329 



magnesium sulphate or ammonium cnloride) by the prolonged action of 

 a feeble galvanic current ; th iron may be then obtained as a dense 



process, because sulphur and phosphorus do not burn out like carbon, silicon, and 

 manganese. 



The presence of manganese enables the sulphur to be removed with the slag, and the 

 presence of lime or magnesia, which are introduced into the lining of the converter, 



loo 50 ; tt o t J sMeter 



yiO. 94. Bessemer converter, constructed of iron plate and lined with ganister. The air is carried 

 by the tubes, L, O, D to the bottom, M, from which it passes by a. number of holes into the con- 

 verter. The converter is rotated on the trunnion d by means of the rack and pinion H, when it 

 is required either to receive molten cast iron from the melting furnaces or to pour out the steel. 



facilitates the removal of the phosphorus. This basic Bessemer process, or Thomas 

 Oilchrist process, introduced about 1880, enables ores containing a considerable amount 

 if phosphorus, which bad hitherto only been used, for cast iron, to be used for making 

 vrought iron and steel. Naturally the greatest uniformity will be obtained .by re-melting 

 the metal. Steel is re- melted in small wind furnaces, in masses not exceeding 80 kilos ; 

 a liquid metal is formed, which may be cast in moulds, A-tnixture of wrought and cast 

 iron is often used for making cast steel (the addition pf a small amount of metallic Al 

 improves the homogeneity of the castings, by facilitating the passage of the impurities 

 into slag). Large steel castings are made by simultaneous fusion in several furnaces and 

 crucibles ; in this way, castings up to 80 tons or more, such as large ordnance, may be 

 made. This molten, and therefore homogeneous, steel is called cast steel. Of late years 

 the Martin's process for the manufacture of steel has come largely into use ; it was 

 invented in France about 1860, and with the use of regenerative furnaces it enables large 

 quantities of cast steel to be made at a time. It is based on the melting of cast iron with 

 iron oxides and iron itself for instance, pure ores, scrap, &c. There the carbon of the 

 cast iron and the oxygen of the' oxide form carbonic oxide, and the carbon therefore 

 burns out, and thus cast steel is obtained from cast iron, providing, naturally, 'that there 

 is a requisite proportion and corresponding degree of heat. The advantage of this 



