GENEKAL DIFFUSION OF COPPER AND ARSENIC. 45 



(Proc. Brit. Assoc. 1849, Amer. Journ. (2) vii, 276, and Journ. 

 Fr. Inst. (3) xvii. 71), seemed to prove that not only carbon, but 

 even silicium had been extracted. This startling assertion 

 needs further investigation ; for, should it be confirmed, the 

 present modes of making bar-iron and steel may eventually 

 give place to, or be modified by, processes of cementation. 



Steel from Bar-iron. — It would be an important addition to 

 the metallurgy of iron, if we possessed a rapid, economical, and 

 efiicient method of partially converting wrought-iron into steel ; 

 for iron may be more conveniently forged than cast into 

 many forms, and, if they were then steeled externally, or at 

 certain required points, Avould possess a core of tough metal 

 with an exterior capable of being hardened. Hence, patents 

 have issued and processes been proposed to efiect this object ; 

 but we may conclude that the experiments have not been suc- 

 sessful, since they have not come into general use. Charcoal, 

 mixed with a little borax, salammoniac and saltpeter, has 

 been proposed (Lond. Journ. xxxvi. 26) as a material to imbed 

 articles forged of iron. As prussiate of potash has a marked 

 effect in converting iron into steel, a bed of charcoal imbued 

 with a solution of the prussiate might answer the desired end. 

 The greatest difficulty lies in limiting the depth of the trans- 

 formation into steel, since the depth seems to depend on the 

 length of cementation, so that large and small pieces cannot 

 be cemented at the same time in the same bed. 



2. Copper. — This metal, one of the next in value to iron, is 

 chiefly furnished by Cornwall, England, where, as in most 

 other localities, it occurs in the form of pyrites, or sulphuret 

 of iron and copper. The same ore has recently been found 

 at Perkiomen, on the Schuylkill River, near Philadelphia, in a 

 good vein. The native copper formations at Lake Superior 

 are truly gigantic ; but if past experience be our guide, they 

 will continue to yield profitably during a lengthened period 

 of time, only when veins of pyrites shall have usurped the 

 deposits of the native metal. 



Copper and Arsenic, their general diffusion. — (Moniteur 

 Industriel, 1846, — Dingler's Journ. ciii.) Walchner finds that 



