Mr. J. Taylor's Lecliires on Mtiallurgt/. 151 



With such motives, great ardour, and often with a hirge 

 share of real chemical knowledge, it is not to be wondered at 

 that the adepts, as they were called, made many discoveries and 

 inventions, and that modern times should have benefited by 

 them. The treatment of the ores, and the reduction and the 

 processes for refining the metals, have therefore long been con- 

 ducted with expertness ; though it may be due to the great 

 improvements in chemical science of later times, that we are able 

 to explain satisfactorily the principles on which they depend. 



To come to a complete understanding relative to the pro- 

 cesses of smelting, or the reduction of the ores so as to obtain 

 the pure metals, we must bear in mind the compound nature 

 of these substances ; observing. First, that all the ores are 

 much mixed with earthy matter even after the operation of 

 dressing or washing, which has been described, so that these 

 earthy parts often bear a large proportion to the whole. 



Secondly', That volatile mineralizers, or substances which 

 may be dissipated or evaporated by heat alone, enter in most 

 cases into the composition of the ores. These, as has been 

 mentioned, are sulphur, arsenic, carbonic acid, as the most 

 common, and having therefore considerable mfiuence on the 

 processes. 



Thirdly, That other substances are found combined with 

 the metals which cannot be evaporated simply, but may be 

 separated by the addition of other bodies to which they have 

 gi'eater chemical affinity. These are first and principally oxy- 

 gen, and occasionally some acids. 



Lastly, That the metals being obtained when the foregoing 

 admixtures are got rid of in a state of union one with the other, 

 or at least to a certain extent, it must follow that, to have 

 the one which we want in a pure state, the others should be 

 separated or destroyed. 



The processes whicii are employed for all these objects are: 

 Calcination or roasting ; 

 Fusion or melting; 



Refining, which is performed in several modes. 

 All these operations reciuire tlie application of heat; and in 

 most of them it is urged to a great degree of intensity. 



The furnaces employed are of two classes : — Blast furnaces, 

 where the fire is excited by the use of bellows or air cylinders 

 constantly working ; and air furnaces, where the effect is pro- 

 duced by strong tiraught, occasioned by the height or construc- 

 tion of the stacks or ciiimneys. 



Blast furnaces arc almost entirely employed in the reduction 



of the ores of iron, and are l()r that purpose constructed o. 



[i L 2 large 



