3(50 UOMAIN IV. TALCOUSi 



rounded part of a copper instrument, it receives 

 the mark of the metal. It is by these characters 

 that it is distinguished from the blackest and 

 most compact argillaceous schisti; they being 

 always scratched by copper^ and never receiving 

 any mark from it, however applied; besides, 

 schisti do not melt like corn&enne. 



" It is on the property, which the Lydian 

 corneenne possesses, of receiving the mark of cer- 

 tain metals, that the use that is made of this 

 Stone, to judge by sight of the quality of gold, 

 is founded. It is vulgarly called touch-stone*. 

 It has also the name of Lydian, because the 

 ancients gave that name to touch-stone; but it 

 no longer comes from Lydia. Those at present 

 used come from Bohemia, Saxony, and Silesia. 

 I dare not however affirm that the touch- stones 

 of those countries are all related to this variety 

 of corn&enne. It is even probable that the 

 greater part among them are basalts. 



<( The Lydian cornfemie, of which we are here 

 treating, is that used as a touch-stone among 



(f * Touch-stones, and the manner of using them, will be spoken 

 of more in detail in treating of the uses of gold. It is probable that 

 different kinds of stones are used as touch-stones, schistus, schistose 

 jaspers, and perhaps even basalts. Wallerius thought he distin- 

 guished three kinds of touch-stones, which he referred to three kinds 

 of rocks, basalt, schistus, and corntenne" 



