On the Origin and Discovery of Iron. 251 



In this improved state of the process, two distinct species of 

 cinders, or scoria, were produced. First, in the smelting of 

 the ores, which from the imperfect reduction contained about 

 20 per cent, of oxide of iron mixed with the earthy matter of 

 the ore; — secondly, in the refining part of the operation, 

 where the scoria produced contained irom 70 to 80 per cent, 

 of oxide of iron mixed with the earthy matter of the ores, and 

 the vitrid waste of the interior of the furnace. 



Abstractedly considered, the operation of the blast-bloomery 

 furnace must be pronounced strictly philosophical, whereby 

 was effected the double purpose of smelting and refining, in 

 both of which large quantities of iron originally contained in 

 the ore were lost. The operation itself, when well performed, 

 was the mean between two extremes, which it must have been 

 the interest and the anxiety of the smith to avoid. If the fur- 

 nace was charged with too small a proportion of charcoal, or 

 too large a relative quantity of iron ore, several evils would 

 follow ; — a lack of heat, a want of proper carbonation, and an 

 imperfect fusion or separation ; masses of ore would pass the 

 blast unmelted, and mingle with the crude iron that had been 

 reduced from the smaller masses of ore, presenting to the ope- 

 ration of refining an imperfect and imhomogeneous surface. 

 On the contrary, an extra dose of charcoal, or a lessened X'ela- 

 tive proportion of ore, would lead to consequences the reverse 

 of the former ; under a higher temperature, an extra dose of 

 carbon would unite with the iron, which would be precipitated 

 on the bottom in a state too fluid for the usual length of time 

 appropriated to the refinement. To divest the iron of its ex- 

 tra dose of carbon, the bellows would be directed upon its 

 surface for a much longer time before it began to coalesce, or was 

 tough enough to break up with the bars, a larger quantity of 

 cinder would be discharged, and less of metal proportionate 

 to the length of refinement. 



When the operation was performed in the most perfect 

 manner, not more than one-half of the iron was obtained from 

 the ores. Tliis gave rise to an innnense accumulation of scoria, 

 which in after ages, and subsequently to the invention of the 

 blast-furnace, became a source of great wealth to the pi-oprie- 

 tor of land, who occasionally under ancient forests, or the 

 deepest soils, discovered large (juantities of these cinders, which 

 were eagerly purchased by the smelters and used in the blast 

 furnace, in mixture with ores, for the production of cast-iron. 



Notwithstiuiding the small produce which in foruter times 

 was obtained from the ores smelted in the blooniery furnace 

 with charcoal as fuel, the late Colonel Fullarton attempt>.d to 



I i 2 inlrodute 



