/:!//:. v\. I--.K.S. 369 



fn I fit- discussion of the Paper 



ON THE USE OF STEEL FOR MARINE BOILERS 



AND SOME RECENT IMPROVEMENTS IN THEIR 



CONSTRUCTION," by W. PARKER, 



I )u. Si KMKXS* slid, I think this paper of Mr. Parker's has brought 

 us some very important matter, and the questions arising 

 upon it have been so well discussed already that I feel it is almost 

 unnecessary for me to say anything. 



The Chairman. There is a question upon which you can give 

 us some important information, namely, whether the thing called 

 steel and the thing called iron exist any more as separate 

 existences ? 



Dr. Siemens. Chemically the only difference is, that what we 

 call mild steel is pure iron it is more essentially iron than what 

 is sold as such ; but as regards the physical properties of the 

 material, it differs in many points from iron and ought not to be 

 confounded with it, because if we were to call it iron and confound 

 it with iron, we should think it right to treat it in the same 

 manner, whereas it requires in many respects different treatment. 

 In fact, Mr. Parker has given you one or two instances. I had 

 occasion to allude at another place to one point which was brought 

 before my notice very forcibly with regard to the steel boilers 

 which Mr. Boyd has constructed. After testing samples of the 

 plates that were supplied by the manufacturers the rumour was 

 spread that the material was wholly unreliable that instead of 

 breaking through the riveted seam, through a narrow strip of 

 metal, it broke through a line of 50 per cent, greater extension 

 rather than through the narrow place ; and as iron would not 

 have given way in that manner, and as the experience of engineers 

 has been derived from iron, it was at first concluded that the new 

 material was not reliable ; but it was soon discovered upon further 

 investigation that the method of riveting employed had been such 



* Excerpt Transactions of the Institute of Naval Architects, Vol XIX. 1878, 

 pp. 188-190. 



VOL. I. B B 



