Dr Colquhoun on the Argillaceous Ore of Irmt. 79 



a state of liquidity. Every substance resorted to with this 

 intention is termed in the metallurgic art, <ijiux, and it is one 

 of the most interesting parts of the art of manufacturing iron 

 to investigate the nature of fluxes, and the manner of employ- 

 ing them. It generally happens, that, by a judicious inter- 

 mixture of diff*erent kinds of ironstone in the furnace, the pre- 

 ponderating earthy ingredient in one has the effect of a flux 

 upon the preponderating earthy ingredient in the others : and 

 thus, by the mutual action of the constituents of two or more 

 ores amongst each other, the earthy ingredients of the whole 

 are simultaneously resolved into a liquid, and the extricated 

 metal of each flows into a common mass at the bottom of the 

 furnace. But it is very seldom that these earthy ingredients, 

 in their state of natural commixture with their respective ores, 

 can admit of having their requisite proportions so accurately 

 adjusted, as to flux each other thoroughly and completely ; 

 and it becomes therefore necessary to introduce into the fur- 

 nace some earth, whose exclusive and important function it is, 

 to effect the complete fusion of the other earthy ingredients, 

 and which is on that account termed a flux. We shall first 

 consider the nature of the fuel which is used by the smelter, 

 and next that of his fluxes. 



1. On Fuel 

 A short space of time only has elapsed, since the charcoal 

 obtained from wood constituted the material which was in uni- 

 versal use, for the purpose of deoxidizing iron ores, and for 

 supplying the carbon by which the reduced metal is subse- 

 quently converted into cast iron. But the manufacture of 

 cast iron must always be in a very imperfect condition, where- 

 ever the operations of the blast-furnace are entirely dependent 

 upon wood charcoal. The cast iron produced by that carbo- 

 naceous material, although eminently adapted for the manu- 

 facture of malleable iron or of steel, is intrinsically far less va- 

 luable than that produced by the coke of pitcoal. It cannot be 

 remelted, and cast into moulds with the same facility and ad- 

 vantage as the latter, being less fusible, and being more ra- 

 pidly decarburetted and converted into pure or malleable iron, 

 when kept for some time in a state of fusion. Nor, under such 

 circumstances, could the manufacture of cast iron ever become 



