I 188 | 



ceffarify to be tried that way. To this purpofe ijt 

 h beft to make a little hole in the charcoal to pujt 

 the Fluor in, and then to put another piece of 

 charcoal as a covering upon this, leaving only 3, 

 Imall opening for the flame to come in at, and to 

 look at the proof As this ftone will neverthelefs 

 moftly fplit and fly about, a larger piece thereof 

 than is before- mentioned, (Seel:, xvi,) mull be 

 taken, in order to have at leaft fomething of it 

 left. 



But if the experiment is to be made upon £ 

 ftone whofe effects one does not want to fee in the 

 ffceper fe, but rather with fluxes, then a piece of 

 it ought to be forced down into melted borax, 

 (Sect.xxiii.) when always fome part of it will re- 

 main in the borax, notwithstanding the greateft 

 part may fome times fly away by cracking. 



SECT. XVIII. 



As the ftones undergo great alterations when 

 jexpofed to the fire by themfelves, whereby fome 

 of their characteriftics, and often the moft princi- 

 pal, are difcovered, they ought firft to be tried 

 that way, obferving what has been faid before 

 concerning the quantity of the matter, direction of 

 the fire, &c. The following effects are generally 

 £he refults of this experiment, viz. 



i. Calcareous earth or ftone, when it is pure, 

 does never melt by itfelf, but becomes white and 

 friable, fo as to break freely between the fingers $ 

 md y if fuffered to cool, and then mixed with 

 water, it becomes hot, juft as common quick lime, 

 As in thefe experiments only very fmall pieces are 

 >}fed,. (Sect, xvi.) this laft effect is bed difcovered 

 by putting the proof on the outfide of the hand, 

 w'&k a drop of water to if, when inftantly a very 



quick 



