Experiments re/peeling "Heat. 263 



different from the diamond, needs no other proof than their 

 incombuftibility. 



One which weighed ' 4 ths of a carat, expofed to the heat 

 for 2 V , was found to have loft no weight; whereas a diamond 

 of the fame fize would in that time have been entirely ditli- 

 pated, and refolved into carbonic acid gas. The ftone loft 

 its tranfparency, and affumed the appearance of a piece of 

 white enamel : it had evidently'begun to fufe, but fome traces 

 pf its form, and even of its facets, are ftill difcernible. 



XX. Another jargoon, weighing ',7 ths of a carat, was 

 expofed to the heal for the fame length of time. It broke 

 into three pieces while under the blaft, but now prefents the 

 fame appearances as the former. The furfaces of both are 

 more opake and white than the interior. 



Vermilions. 



XXI. A vermilion which weighed ^-ths °f a carat, treated 

 for 2', loft no weight, but became fufed into a polifhed opake 

 globule, which is nearly black, with a tinge of brownifh- 

 green, like that of very dark bottle glafs. 



XXII. Fourteen vermilions, weighing §|ths of a carat, 

 expofed for 2 SO"* were completely fufed into a poliftied 

 opake globule, very like the former, but not quite fo dark. 

 It is alfo not fo round or poliftied, having been preffed while 

 foft. A fmall face being afterwards fubjected to the lapidary's 

 wheel, the ftone appeared as hard as at firft, but not fufcepti- 

 ble of fo high a polifh. 



Garnet. 



XXIII. One which weighed i^-ths of a carat, expofed to 

 the blaft for 1/ 40', broke in two pieces, both of which be- 

 came fufed. The largeft prefents an appearance very like 

 that of the vermilion No. xxi. ; the other is of a dark lead 

 colour inclining to a bronzy hue and chatoyant, fomewhat 

 like peacock-lead ore. Both were preffed while foft; the 

 latter fo much fo, that it at prcfent retains nothing of a glo- 

 bular form. 



Emeralds. 



XXIV. One, of the weight of §£ths of a carat, was fufed 

 in 2 into a globule of an opake white colour without any 



lofs 



