2IO THE SCIENTIFIC PAPERS OF 



The regenerative gas furnace, which is the joint production of 

 my brother, Frederick Siemens, and myself, is already known 

 through its application to nearly all those branches of industry in 

 which furnace heat is employed. It was described by Faraday, 

 to the members of the Royal Institution, in the last public lecture 

 delivered by that great philosopher in 1862, and has since been 

 the subject of several publications. I need not, therefore, bring 

 before you all the features of this mode of producing intense heat 

 for the various purposes to which it has been applied, but shall 

 confine myself to its description as applied only to the production 

 of cast steel in large masses, which is the principal subject of my 

 present communication. 



NATURE OF STEEL. Before proceeding with this description I 

 shall briefly remark upon the nature of steel and the methods by 

 which it has hitherto been produced. 



STEEL. Steel is generally regarded as a compound of iron and 

 carbon, possessing the remarkable quality of becoming exceedingly 

 hard when heated and suddenly cooled. The proportion of carbon 

 determines the degree of hardness of which the steel is capable, or 

 what is termed its temper. 



The following table of the percentage of carbon in steel suited 

 to different purposes, is prepared from analyses made in my 

 laboratory by Mr. A. Willis, unless another authority is men- 

 tioned. 



Description. Carbon per cent. Authority. 



Wootz . ' . . . . 1-34 T. H. Henry 



Steel for flat files . . . . T2 A.Willis 



for turning tools . TO 



,, (Huntsman's) for cutters .1*0 



., for cutters .... '9 



for chisels .... "75 



Die steel (welding) ... '74 



Double shear steel .... '7 ,, 



Welding steel .... '68 



Quarry drills *64 ,, 



Mason's tools ... '6 



Ramrods '6 ., 



Common steel for stamping . '42 



