53^ On the Comndum Stone from Afia, 



aftion of heat, and I found, on pouring the muriatic acid on the fubftance, when cool, that 

 there was a great difengagement of fulphurated hydrogenous gas. 



I filtered this folution in muriatic acid, and I found the cryftals exaflly fimilar to thofe 

 which I had often formed, by adding the muriatic acid to the flrontian eartli, found in Scot- 

 land. This muriate poflefl'ed the property of changing the flame of the candle to a moft 

 beautiful red colour. A copious precipitation was formed, when the fulphuric acid was 

 added to a folution of this muriate. From thefe experiments, and from the external charac- 

 ters of the ftone, I have no hefitation in believing, that it is compofed of the fulphuric acid 

 and ftrontian earth. 



P. S. Should you wifli to poflefs a fpecimen of tliis fubftance, on receiving a line from you, 

 I will take tlie firft opportunity of fending one to you. 



III. 



On the Corundum Stone, from Afia. By the Right Honottrable CHARLES GREFILLEy F. R. S. 



(Continued from p. 485, Vol. II.) 



M. 



LR. Tranckell, who refides in Ceylon, and from whofe communications I derived lately 

 much information, had, about five years ago, a fapphire, the greater part blue, and the re- 

 mainder of a ruby colour. I faw, in Rome de L'Ifle's colledlion, at Paris, a fmall gem, which 

 was yellow, blue, and red, in diftinft fpots, and he called it oriental ruby." M. de la Metherie, ta 

 avoid the confufion of the denomination oriental ruby, with oftoedral ruby, calls it a fapphire : 

 with more corre£tnefs, I think, the above-mentionened gems fliould be clafled as argillaceous, 

 under the denomination of corundum. I am not uninformed, that corundum is faid to be 

 found in France. The Count de Bournon is convinced, that the fpecimens mentioned in 

 Crell's Journal, as having been found by him in a granite in the Forez, were corundum. M. 

 Morveau alfo fays, he found it in Bretagne ; but the Abbe Hauy, in No. 28, of the Journal 

 des Mines, aflerts, that the corundum, found in France, is titanite ; he docs not fay whether 

 this obfervation extends both to the corundum of Bretagne and that of the Forez. In the 

 fame manner I had obferved in the fpecimens, which Mr. Rafpe called jade, or a new fub- 

 ftance from Tiree, on the weft coaft of Scotland, a great refemblance to corundum ; but, hav- 

 ing then only had a curfory view of the fubftance, I am indebted to Mr. Hatchett for the 

 examination of a fpecimen of it, which he had from Mr. Rafpe's colleftion. The Tiree ftone 

 lefembles cryftallized corundum of the coaft, in texture and colour ; it is alfo as refraftory, 

 when examined by the blow-pipe, with different fluxes. Its fpecific gravity is 3,049; confe- 

 quently nearer the fpecific gravity of pure corundum than the above-mentioned lump, 2,785, 

 and the matrix of corundum, 2,768. The Tiree ftone will fcratch glafs readily, but not rock 

 eryftal j Its hardnefs, therefore, correfponds with that of the matrix of corundum. The 

 fubftance of the lump, defcribed in page 481, cuts glafs and rock eryftal, and the Tiree 

 ftone, readily. 

 It will, therefore, be fufficient for me to fay, that there is great probability corundum may 



be 



