340 THE SCIENTIFIC PAPERS OF 



metal in nitric acid and observing the effect of colour on the solu- 

 tion. The nitric acid did not act upon the carbon, and it produced 

 a brown tinge of sufficient intensity to be distinctly observable, 

 even though the proportion of carbon should be considerably below 

 O'l per cent. This test would enable manufacturers to produce 

 steel of extreme mildness, such as was now used largely for engi- 

 neering purposes. It was impossible to estimate so slight a differ- 

 ence in carbon as 0'05 or O'l per cent, by any mechanical test ; 

 but by a ready chemical test of that kind the manufacturer was 

 enabled to bring the metal down to an exact point considerably 

 below O'l per cent. No doubt these questions were at present 

 only partially understood, and much work was still required in 

 order to arrive at certain conclusions regarding the conditions 

 necessary to produce steels of definite qualities. If steel was pro- 

 duced from pure iron, such as was found in Sweden, a metal could 

 be made containing hardly any manganese, and only a trace of 

 carbon, and no appreciable percentage of phosphorus or silicon ; 

 and metal of that description, which was as nearly as possible of 

 pure iron, was perhaps the toughest that could be made, exceeding 

 in toughness copper or even silver. A further advantage of such 

 metal was that it was less liable to rust. Experiments lately made 

 in France showed a percentage of rust, as compared with wrought 

 and cast iron, in the proportion of 0'4 to 1'4, being much in favour 

 of a pure metal such as a very mild steel a quality of great value 

 for shipbuilding and purposes of that kind. 



SOME FURTHER REMARKS REGARDING THE PRODUC- 

 TION OF IRON AND STEEL BY DIRECT PROCESS. 

 BY MR. C. WILLIAM SIEMENS, D.C.L., F.R.S.* 



IN mixing comparatively rich iron ore in powder, with about 25 

 per cent, of its weight of pounded coal, and in exposing this mix- 

 ture for some hours to the heat of a common stove or of a smith's 



* Excerpt Journal of the Iron and Steel Institute, 1877, pp. 345-359. 



