XAGNESIAN EARTH. 277 



A phial thus prepared may be ufed every night for fix 

 months: there is no danger of fire from it, and its coft is very 



fmall. 



• XVII. 



Jnalyfis of the Magnejian Earth of Baudiffero in Canavais (in 

 the Department of the Loire,) known by the Name of Porcelain 

 Earth, and hitherto confidered as a Clay, By M. Giobert.* 



JL HE earth of Baudiffero, known by the name of porcelaih Porcelain earth 



earth, has been hitherto confidered as one of the pureft ar^il- co ° fider f d *! 



t " native alumine. 



iaceous earths known in the hiftory of foflils, and is arranged 



in our cabinets of minerals as native alumine. 



In a manufacture of ftone-ware pottery, which has been ufed as fucfc ia 

 eftablifhed at Vineuf, this earth has been ufed for a long time, the ft°ne-ware 

 *s a clay of extraordinary purity. The celebrated Macquer, neu f. 

 and with him Baume, to whom fpecimens of this earth were 

 fent from the above manufacture, pronounces poiitively that it Various chemift* 

 was a clay of fuperior quality to that which they ufed in the ^^{j* fam * 

 manufactory of porcelain at Sevres. 



Doctor Gioanetti continued to ufe it in the manufacture of 

 fcis fine porcelain at the fame Vineuf; and he engaged in, if 

 not ananalyfis, at leaft fome experiments on this earth, to at- 

 certain raore precifely the proportions in it between (ilex and 

 earth, which he believed to be pure alumen. Thefe experi- 

 ments convinced Doctor Gioanetti, that, with the exception 

 of a little carbonic acid which he found in it, the earth of 

 Baudiffero was an alumen almoft perfectly pure, or at leaft the 

 pureft that he had ever met with. 



This chemift, when I made enquiries of him relative to The alumine 

 this earth, allured me frequently, that picked pieces yielded J£ s * ~JJJ* 

 him fometimes ninety per cent, of alumen, including a little 

 carbonic acid, and that in the grofs it yielded conftantly at 

 leaft 80. - 



On the perufal of the mineralogical defcfiption of the moun- Other authorl- 

 tains of Canayvais by the Chevalier Napion, it will be found **• 

 ihat this eftimable mineralogift has not hefitated to declare the 



* Journal de Phyfique, LX» 



earth. 



