248 



ON THE MINES AND MINERAL 



It is, however, in the roasting, and smelting operation, that the great- 

 est room for improvement is to be found ; and the greatest prospect of 

 advantage from a change; as the immediate effect of this would be, to raise 

 the value of the metal produced. For the present open hearths, and air 

 bags ; I would substitute a system of reverberatory furnaces ; of different 

 draughts, for the two different processes, of roasting and smelting. An 

 excellent material for constructing them is at hand, in the rock, I have cal- 

 led potstone. Perfectly compact, and equal to any resistance ; infusible 

 in the strongest heat ; while it is so soft as to be cut with a knife ; it is 

 difficult, even to imagine, any substance better fitted for such work. It 

 might be advisable, in an economical point of view, to construct the roast- 

 ing furnaces in such a manner, as to collect the sulphur at present lost ; 

 an object not difficult to be effected. 



Even the introduction of the simple blast furnance used in Chili, (and no- 

 thing can be simpler) would be an immense improvement. It is of a circular 

 shape ; similar to a lime kiln ; and covered with a dome, to confine and con- 

 centrate the heat. The ore is arranged in it, in alternate layers with the fuel, 

 which is wood ; and being lighted, it continues burning for a considerable 

 time. When required; the heat is urged by a double pair of bellows, work- 

 ed by a crank, turned by a water mill. The mere substitution of an efficient 

 bellows, for the air bags, used at present, would be no trifling advantage 

 gained; but I am of opinion, that a wind furnace is greatly preferable to 

 all these half measures, in the saving of manual labor. Nor is it so much 

 inore expensive, even at the outset, as might be imagined. 



The methods of reduction practised in England ; where, certainly, the 

 subject is best understood; vary with the ore, and even with the establish- 

 ment : but the differences are trifling, and affect only the minor details. The 

 two great objects to be effected, are — first, by a properly regulated heat to 



drive 



