76 Br Colquhoun o7i the Argillaceous Ore of Iran. 



may be truly denominated the basis of the most interesting of 

 all our metals, the material for the most important of all our 

 manufactures, and the most powerful instrument in the hands 

 of civilized man for advancing the arts, and for adding to the 

 comforts of the species. It probably has been by an applica- 

 tion of some of the more elementary processes of chemistry, 

 that simple fusion was first employed to extract the iron from 

 the ore in which it was concealed. The manifold uses of the 

 developed metal could not fail to command the continued and 

 eager attention of men, as soon as its extrication was first dis- 

 covered. And a long and careful experience has at length car- 

 ried forward to a stage of very considerable advancement, the 

 art of mingling in the furnace, along with the ores, such foreign 

 bodies as have been found best fitted by their individual or 

 combined chemical properties, for aiding the action of heat, in 

 extricating the pure metal. And besides this, owing to the 

 same power which different sorts of earthy matter possess of 

 mutually fluxing one another, it has been discovered that when 

 two ores, each of which smelted separately would yield its iron 

 with the greatest reluctance, are taken and fused together, they 

 not unfrequently give up the joint product of both their metals 

 with comparative ease. 



In viewing the ironstone, then, as a subject of the metallurgic 

 art, and in selecting those varieties to each of which the same 

 fluxes will be available, we shall find that it may be subdivided 

 as follows. 



1. The pure carbonate of iron. — Under this head, the 

 smelter will comprehend all those ores in which the extra- 

 neous ingredients are too small in amount to be capable in any 

 sensible degree either of favouring or of resisting the liquefying, 

 operations of the blast-furnace. It is rare to met with ores 

 thus constituted ; for they are generally combined with some 

 earthy ingredient requiring a peculiar flux. Of these extrin- 

 sic bodies the most common are bitumen or coal, sand, clay, 

 lime, and magnesia. But the sand or clay frequently occur 

 not singly, but mixed with large proportions of carbonate of 

 lime ; and all these three substances are often found united 

 with a very considerable amount of bitumen. According to 

 the manner in which the ore presents itself, as combined with 



