WILLIAM SIEMENS, F.R.S. 



395 



tlir finder is discharged ; the tapping-hole is thereupon closed 

 again, and the furnace made to rotate somewhat more rapidly with 

 a \ ifw of facilitating the agglomeration of the metallic iron ; by 

 tin- timely introduction of a rabble, the agglomeration of the mass 

 can be so regulated as to induce the formation of two or three 

 balls of convenient size for handling. The balls being formed, 

 the furnace is stopped with the large door in its lowest* position, 

 which, upon being removed, admits of the charge being withdrawn. 

 This is effected by the introduction of tongs supported by pulleys 

 running upon overhead rails for transferring the balls in rapid 

 succession from the furnace to a squeezer (which has for its purpose 

 to expel adhering cinder), and from the squeezer to the bath of 

 such a steel melting-furnace as already described. 



The great purity of the metal thus reduced from the ore, and 

 the rapid and comparatively inexpensive nature of the reducing 

 process, are conditions highly favourable to the production of steel 

 of high quality by this method at reasonable cost ; and it is my 

 intention gradually to complete the open-hearth process of pro- 

 ducing steel by combining with it the mode of preparing the 

 material to be melted just described. 



What I also wish on this occasion to call attention to are certain 

 properties of steel which are of importance in considering its 

 applicability to engineering and military construction. We know 

 that steel varies between very large limits in its hardness and in its 

 ductility, but it is not so generally known that steel up to a 

 certain point is of the same strength to resist strain when it is mild 

 as when it is hard, and I have prepared a table of results which 

 shows very clearly the nature of both mild steel and hard steel if 

 compared under different strains. 



Upon reference to the table it will be seen that loads from G to 

 15 tons per square inch affected all the bars equally, whether hard 

 or soft, annealed or unannealed, and with the exception of one bar 

 only this uniformity holds good up to 18 tons ; up to this limit, 

 the elastic elongation of all the samples was equal ; but with the 

 strain of 18| tons, the mild steel has become permanently elongated, 

 whereas the harder steel shows a normal increase of elastic elonga- 

 tion. With the hard bars experiments were continued, and 21 

 tons to the square inch was applied, producing an elastic elonga- 

 tion '108, which is entirely normal, and no permanent set is pro- 



