214 THE SCIENTIFIC PAPERS OF 



sidered of good quality when it bears seven times its own weight, 

 and the famous Haarlem magnet of the same weight, supports 

 about 13 times its weight, I am now able to produce a similar 

 horse-shoe magnet carrying 20 times its weight, suspended from 

 its armature. 



The chief difficulty besetting experiments on the effects of 

 these various admixtures upon the quality of steel, consists in 

 the unavoidable presence of other substances in variable propor- 

 tions ; but the effects of these other substances could be eliminated 

 if the experiments were accompanied by exhaustive analyses, and 

 it is impossible to over-estimate the advantages that would result 

 from such a course. 



PROCESSES. Dr. Percy, in his truly invaluable metallurgical 

 work, has made us acquainted with the various known processes 

 for obtaining steel which have been followed from the earliest 

 times ; but no method of producing steel can be considered 

 admissible at the present day which does not pass the metal 

 through the condition of entire liquefaction, for it is only by 

 fusion that foreign admixtures can be thoroughly separated, and 

 that flaws and fissures can be avoided ; inasmuch, however, as the 

 steel obtained by tiiem may be subsequently fused, I shall briefly 

 refer to them. The principal processes of this class are : 



1. The direct process of making steel, or steely iron, from the 

 ore in the Catalan forge, by employing a large excess of charcoal. 

 The steel is obtained without fusion in the form of a ball of 

 spongy metal, and is drawn out into bars. 



2. The cementation process, in which bar-iron is converted into 

 steel by prolonged contact at a comparatively low temperature 

 either with liquid cast-iron, as formerly practised in Styria and 

 elsewhere,* or with crushed charcoal a method extensively em- 

 ployed in Sheffield at the present day for the manufacture of 

 steel for railway and carriage springs, and for the production of 

 bar-steel from Swedish iron, which, when subsequently melted in 

 pots, makes the finest quality of steel for tools and cutlery. 



3. The decarburization process, in which steel is made from 

 cast-iron by the removal of part of the carbon in the puddling 



* Percy, Metallurgy, II. 790, 807. 



