2 8 Experiments re/peeling Heat. 



XIV. Eight more, weighing i 5 6 T carat, heated for < j / 8", 

 loft no weight : they were agglutinated, like the former, into 

 a fhapelefs mafs (which afterwards broke in two), with the 

 fame appearance of a whitifh vitreous matter interpofed. One 

 fmall portion of the furface ftill retained a fine polifh. An- 

 other part of it was afterwards polifhed by the lapidary : the 

 ftone was found to be as hard as before. 



XV. To prove whether a longer expofure would not pro- 

 duce a more perfect fufion, feven more, which weighed to- 

 gether half a carat, were fubje£ted to the heat for 9' 2", but 

 without undergoing any other change than that of being fuf- 

 ficiently fufed to be firmly agglutinated together by a white 

 vitreous cement : the colour of the ftones themfelves remains, 

 in a certain degree, unaltered. 



XVI. Nine rubies, weighing -£*ths of a carat, were in- 

 tended to be expofed for a ftill longer portion of time, but, 

 after 6' 10", were obferved to be in fufion. They were then 

 withdrawn, and the mafs weighed, but no lofs of weight was 

 perceptible. They now compofe an opake, dirty-looking, 

 whitifh mafs, fomewhat like melted camphor, and which 

 has evidently been perfe6tly fufed. A few fmall portions 

 ftill retain fomewhat of their original colour ; but would 

 probably, alfo, have become white or gray, by a longer con- 

 tinuance of the heat. 



It is, perhaps, worthy of observation, that a happy acci- 

 dental arrangement of the fubtiances employed, will fome- 

 times produce inftantaneoufly more powerful effects than a 

 longer expofure under other circumftances. This was the 

 cafe in the prefent inftance ; for the weight of the rubies ufed 

 in the laft experiment, was to that of thofe employed in the 

 preceding one, as 3 to a, and yet, though the heat was ap- 

 plied for little more than Z-$ds of the time, the effects were 

 much more ft liking. 



Some remark may perhaps alfo be applicable with regard 

 to the white vitreous fubftance into which the furfaces of the 

 ftones become changed. Is it probable that the alkali of the 

 charcoal contrbuted to deftrov the colour of the ftones ? or. 

 Would a carbonaceous fubitance, containing no alkali, have 

 exhibited with them the lame phenomena in all refpects ? 



This, 



