Experiments refptEihig Ihat, ■ 23 



tt mu ft neceflarilv be immerfed in water, neither its coldnefs 

 or humidity hinders the paflage of the globule, .which fcems 

 to make its way through with as much eaie as it would 

 through a piece of writing paper. When the jerk is fefe 

 powerful, the ball of iron will fometimes not go quite 

 through, but lodge itfelf in the fubftance of the glafs, which 

 it in that cafe generally foftens fo as to raife a protuberance 

 on the outride. 



The contemplation of fuch powerful effects of heat as thefe, 

 induced the Society, on the fuggeftion of a very worthy 

 member, and zealous cultivator of the fciences, Mr. Francil- 

 lon, to enter upon the prefent experiments, which were per- 

 formed upon the different fpecies of gems hereafter enume- 

 rated ; for all of which the Society was indebted to the po- 

 litenefs of the gentleman who firft: propofed the fubject, and 

 from whole very valuable cabinet they were accordingly fup- 

 plied. 



The experiments were made in the prefence of the Society 

 at different meetings, from 24th September to 26th Novem- 

 ber 1798, in the order in which they are here mentioned ; 

 the prefent account being compiled from the original mi- 

 nutes taken by Mr. Turton, their fecretary, with that degree 

 of accuracy which ufually characterifes them, and which have 

 again been compared with the gems in their prefent ftate. 



The apparatus employed will be defcribed at the end of 

 the prefent communication. 



Diamonds. 



I. The firft ftone fubjeeted to experiment was a rofe dia- 

 mond of the weight of ~l ths of a carat. It was put upon a 

 piece of compact charcoal in which a fmall excavation had 

 been previously made, and the flame of a lamp, urged by a 

 common blow-pipe, then thrown into the -cavity. When 

 the charcoal was ignited it was prefented to another blow- 

 pipe, fupplied by the gafometer with an uninterrupted ftream 

 of oxygen gas. 



The diamond, at the end of c:.e minute and fifty feconds, 

 was found to weigh only /.[ths, having loft i-Uhs of iu ori- 

 ginal 



