SIX WILLIAM SIEMENS, F.R.S. 403 



the material now used largely in railway structures, both in pro- 



ducing wheel tyres and the rails upon which they run. This 



ial is remarkable for great strength coupled with a sufficient 



i !' toughness to resist very heavy blows, and we now call 



: In- material which exceeds even copper in ductility, stretching 

 as it does 25 per cent, before breaking. Yet I am in favour 

 .f continuing the appellation of steel in speaking of all materials 

 consisting mainly of iron, which are malleable and have been 

 proilucctl by a process of complete fusion. It is to this cir- 

 cumstance of complete fusion that the superior uniformity and 

 the certainty of character of the steel of the present day are due. 

 If we follow the production of wrought iron through all its 



s we almost wonder how even such uniformity of strength 

 and character is produced as we find it to possess. In puddling 

 iron the workman produces about 1 cwt. of metal that has been 

 massed together from a semi-fluid condition, and the nature of 

 which depends upon his skill, the temperature of the furnace, 

 and other variable conditions. The consequence is that one ball 

 is never quite similar to another. One may be what is called 

 young iron, and another is more matured when it leaves the 

 furnace. The young iron will, after consolidation by hammering 

 and rolling, show a crystalline fracture, and the other more en- 

 tirely decarburized material will possess a fibrous texture. In 

 order to harmonize the differences in the character of the iron 

 in successive balls, the process of re-mixing or packeting is re- 

 sorted to, which consists in welding together bars produced from 

 different charges, and rolling them anew. Thus by very careful 

 treatment the inequalities naturally appertaining to puddled iron 

 may be reduced, and iron of high quality, such as Yorkshire 

 plate, may be produced ; but such care is not always taken, and 

 hence arises the uncertain character of the iron of commerce. 

 Even the best commercial wrought iron is not pure iron, but 

 an agglomeration of that metal with cinder (as may easily be 

 seen by viewing a section of a bar through an ordinary magni- 

 fy ing glass), and not unfrequently with more hurtful substances 

 such as sulphur and phosphorus. In producing steel, however, 

 and particularly in producing the steel now used in engineering 

 and architecture, a mass of some ten or twelve tons may be seen 

 in the furnace in a state of perfect fluidity, in which state it 



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