16G On the Origin and Discovcrij i>J' hun, 



heat would easily be regulated by narrowing or enlarging those 

 apertures, and a renewal of the fuel when necessary easily ef- 

 fected by the funnel at the top. Tliis seems the greatest ad- 

 vance in the art which the African has made, and it is highly 

 creditable to the inventive powers of that people, that Alrica 

 is ranked in the class of iron-making nations. Mexico and 

 Peru, with all their claims upon civilization, could not at the 

 time of their discovery boast the possession of such an art. 



In other countries iurnaces of various shapes have been de- 

 vised ; but, however different in structure, they have acknow- 

 ledged the same practice now followed upon the burning sands 

 of Africa. Oblong fui'naces with flues and passages of an en- 

 larged size to conduct and rarify the air, and capable of con- 

 verting more ore at one time, seem to have been the greatest 

 advancement in the air-bloomery : the practice of which un- 

 der every contrivance was to stratify the ore with the fuel ; 

 and the principle, a gradual de-oxidation of the ore whilst it 

 maintained the combustion. A high temperature united or 

 welded the masses of iron ore together ; tliese were carried to 

 a stone, or in the advancement of the art to an anvil, where, 

 by means of hammers, the unmetallized particles, forming with 

 the earths a vitreous scoria, were forcibly expelled, and form 

 given to the metallic mass. This is now principally confined 

 to some of the Spanish provinces, and to the shores of the 

 Mediterranean, where considerable quantities of ore from the 

 Island of Elba are worked in this manner. The remains of 

 furnaces of this sort have been found in elevated situations in 

 Scotland ; and though the form can no longer be traced, yet 

 in the neighbourhood of Dean Forest are the ruins of old fur- 

 naces surrounded with scoria, on the high grounds, where the 

 only apparent mducement for their erection could have been 

 a strong current of air. 



The practice of these air-bloomeries must have been slow 

 in the extreme. A long and continued cementation of the ore 

 in contact with the fuel, must in the first instance have been 

 necessar}' to dispose the metallic particles to unite. A too 

 rapid exposure to a high temperature would be apt to unite a 

 considerable portion of oxygen with the ore, which in this way 

 would acquire a considerable degree of fusibility : this would 

 not only diminish the quantity and quality of the iron, but re- 

 tard the general operation. To render the quality of tlie iron 

 homogeneous^ masses of iron ore would be used as nearly of 

 one size as possible, which would give rise to a rejection, in 

 part, of the small or dust ore generally the richest of the vein. 

 That this practice prevailed to a considerable extent in Glou- 

 cestershire, is evident from the large quantities of small mine 



found 



