.THE SCIENTIFIC PAPERS OF 



bath. In 1863 and 1865 he had tried, moreover, many ex- 

 periments with basic linings, including lime lining, in connection 

 with the open-hearth process, but he never met with such an 

 amount of practical success in his endeavours to render such 

 linings permanent as to justify him in recommending their 

 adoption to his licensees. He believed the Bessemer metal was 

 perfectly good for nearly all the purposes to which mild steel was 

 put, but he was equally satisfied that the open-hearth process was 

 best suited for the production of such special qualities of steel as 

 were now under discussion. 



DE. SIEMENS remarked that with regard to the mysterious 

 breakages which had just been alluded to by Mr. John, perhaps 

 he (Dr. Siemens) had not expressed himself as clearly as he should 

 have wished on the previous day, if he had said that it was owing 

 to its great ductility that steel tore more readily than iron. What 

 he meant to say was, that steel tore more readily because it 

 was the more uniform and more homogeneous metal. In iron 

 each fibre was a place at which a tear would stop. In steel, if a 

 tear was once started, it would run along just as it would, for 

 instance, with india-rubber, the most elastic of all materials. If 

 they took a strip of india-rubber and elongated it ten times, it 

 would return to its original length upon removal of the strain upon 

 it. If, therefore, the edge of the india-rubber was slightly nipped with 

 a pair of scissors, and it was again stretched to the same extent as 

 before, the india-rubber would tear right across from the point of 

 discontinuity produced by the incision. The same kind of tearing 

 action was set up in mild steel, when it was treated in a way that 

 was not suitable to it. In working mild steel drawn out in a 

 half cold state and allowed to set, great tension arose in the mass ; 

 and unless the metal was subsequently annealed, a tear might 

 commence at a rivet hole, and that tear would run along more 

 readily than in iron. Care should be taken to prevent mischief 

 from this cause in dealing with mild steel. 



