[ 3°° ] 



flics *>*ff, when the iron fcorifies : neither can aH 

 <thofe Blendes, which contain filver or gold mi- 

 ;neralifed with them, be tried in this manner, 

 which is particularly owing to the imperfect calci- 

 nation •, nor are the quickfilver ores fit for thefe 

 experiments, the volatility of this femi-metal mak- 

 ing it impoflible to bring it out of the poorer fort 

 of ores * ; and the rich ores, which fweat out the 

 quickfilver, when kept clofe in the hand, not 

 -wanting any of thefe affays, &c. Thofe ores 

 ought to be aflayed in larger quantities, and even 

 with fuch other methods, as cansot be applied 

 £jpon a pierce of charcoal. 



SECT. XXX*V. 



Some ,of the -rich filver ores are eafiiy tried.: 

 for inftance, Minera argenti vitrea^ commonly cal- 

 led Silver-glafs, which confilts only of filver and 

 .fulphur. When this ore is expofed to the flame^ 

 it melts inftantly, and the fulphur goes away m 

 fume, leaving the filver pure upon the charcoal, 

 |n a globular form. If this filver mould -happen 

 fto be of a dirty appearance, which often is the cafe, 

 then it mud be melted anew with a very little 

 borax, and after it has been kept in fufllon for a 

 minute or two, fo as to be perfectly melted and red- 

 hot, the proof is fuffered to cool : it may then be 

 -taken off the coal, and being laid upon the fteel- 

 plate, (Seel. xi. n.) the filver is feparated from the 

 (lag by one or two ftrokes of the hammer (Se£t. xi. 

 £.). Here the .life of the iron ring (Seel, xi.) is 

 manifeft, for this ought firit to be placed upon 

 the plate, to hinder the proof from flying off by 

 .the violence of the ftroke, which otherwife would 



* A piece of gold being laid over tlie proof, to receive the 

 fumes, readily discovers if it contains any quickfilver. And it 

 ;rs probable, that by like proceiTcs, we may alfo be enabled to 

 .di&over *y&h the Blow pipe other of the volatile fubftances. 



happen. 



