in APyri.tes. 155 



ing fulphur, and a metal-earth, but in a production 

 or generation, and thus in an internal ground-union, 

 as has been often mentioned ; where then fuch ac- 

 curate reparations, as that one part lhall not either 

 fwallow up, force over with it, or keep back fome- 

 thing of the other, are neither credible nor pof- 

 fible, the cafe will prove eafy. Again, let us confi- 

 der what a number of times copper mu ft pafs thro' 

 the fire, in roafting and fanelting, 'ere it only be- 

 comes black-copper, whereas iron-ftone fcarce wants 

 a fingle roafting, being directly conveyed to the tall 

 furnace. 



(3. ) Confider only the violence of the degree of 

 the fire in the tall furnace for iron, above that in 

 the furnace for copper ; fo that, by the fudden 

 brifk flux, the fulphur feparates not fo accurately 

 from the metal earth ; but becomes, in fome de- 

 gree, incorporated with the metal ; whereas, by a 

 more gentle fire, it might more accurately and much 

 fooner be feparated than from the copper - 7 as I ob- 

 ferved from meafuring the time for roafting the 

 proofs of copper ores and iron-ftone: tho' there 

 may be inftances where the contrary may happen, 

 and this may be owing to this or the other admix- 

 ture ; yet, it happening more rarely, we muft abide 

 by what more generally occurs. 



Iron, in whatfoever manner treated, does not 

 fo readily as copper admit fulphur. The moft feafible 

 method I know of is, firft, to ignite the metal well, 

 and then convey the fulphur upon it-, when the 

 copper actually mineralifes, entirely lofes its co- 

 lour and metalleity, turns of a grey caft, almoft 

 like a fallow ore, and increafes in weight about a 

 fifth : whereas iron not only remains without the 



lead 



