390 ^'^ i^e AJfayhig of Ores hy Fujion. 



Wctal is fubfequently manuFaftured into bars, it is fiated, a^ 



different places to produce cold and hot (hort iron. 



The kidney ore will admit of a diminution of chalk, and 

 a fmall addition of glafs ; i lb. averdupoife of this variety 

 yijl be accurately aflayed with the addition of 5 oz. chalk, 

 1 oz. of glafs, and 3-4ths oz. of charcoal. The fame pro- 

 portipn of mixtures will alfo accurately reduce the fmall 

 pieces of this ore, commonly of a foft, greafy conliftency, 

 mixed with fmall fragments of the haematites and kidney, 

 and will give out the iron which they contain fuper-carbo- 

 nated. A mixture of this foft ore with kidriey is pTeferrejl 

 to the richer varieties at the iroii manufaftpries. Th^ 

 Lanpaftiire ore chiefly confifts of this coinpoynd, and ihe 

 poorer in jron has ajways a decided preference given it ^ 

 the blaft furnace. 



The ftratified iron ore of the ifland of Iflay is of moil 

 difficult fufion when treated without any addition. It fufes 

 into a blackifh _green ponderous mafs, and, even expofed to 

 the higheft heats, lets fall but a fmall (hare of its iron. The 

 quality thus obtained is in the higheft degree oxygenated; 

 its frafture is partially cryftallifed in lines which converge 

 towards the upper furface of the button, fimilar in cryftal- 

 lifation to the fracture of zinc. A regulus thus obtained, 

 when diverted of its fcoria, and properly expofed to the 

 a6lion of the ignited gas, foon lofes its fluidity, and pafles 

 into the flate cf ftrong malleable iron. If this operation i$ 

 performed upon ^ large quantity, \yithput agitating pr turn- 

 ing the m;»fs, the upper furface of malleable iron will early 

 acquire the cold {hort quality, and will be fubjed, at the 

 fame time, to an uncommon wafte by the rapid oxydation 

 of its parts. In affaying this ore for the produdtion of car- 

 bonated crude iron, the relults are obtained with confiderable 

 difficulty; feldom perfe^S; till the fecond or third experiment. 

 This is chiefly owing to the great variety of quality in the 

 ^ratuip, two pieces feldom being alike either in appearance 

 or in reality. The inferior mafles yield from 44 to 48 per 



