Metals. 241 



softer by these means ; cracks and flaws are pro- 

 duced in it, and of consequence it is more easily 

 divided. 



After all, there will in washing be some loss 

 of the metal : hence it is found more expedient 

 to bring the whole mass into fusion, as is much 

 practised in Germany. The fusion is performed 

 in some of the ordinary furnaces, and commonly 

 with the addition of particular stones, or the 

 scoriae of former fusions, which greatly promote 

 the fusion of the new matter. Thus, the metallic 

 matter settles to the bottom still in the state of 

 an ore, whence the process is called crude sepa- 

 ration, when the ore is thus freed from its ma- 

 trix. The next operations are to separate the 

 sulphur, arsenic, &c., which the metals may 

 contain ; and this must be done by a mild heat, 

 because of their strong adhesion to the metals, 

 which the metallurgists call their rapacity. If 

 exposed to a violent heat, the arsenic will fly offj 

 but when thus forced off intensely it sometimes 

 carries off part of the metal with it. This 

 treating the ore in a gentle heat is called roast- 

 ing it. The workmen commonly build the ore 

 into heaps with fuel, so that the whole may be- 

 come red-hot, and the air have free passage 

 through it. Some ores, as those of copper, re- 

 quire many repetitions of the process, the sul- 

 phur and arsenic adhering so closely. 



In consequence of this operation, the metal 

 remains more or less in the form of an oxide; 



VOL. II. M 



