The BRAZILIAN SfONE. 93 



operations of heat and cold, or the effects of frequent expan- 

 fions and contractions, partially applied. Now, it is precifely 

 the fame ftructure which is required for thofe two purpoies, 

 that of procuring flexibility, and that of refitting fracture by 

 the partial application of heat and cold ; and the two things 

 here compared, the ftelltten and the Brazilian done, are of the 

 fame conftruction, fo far as compofed of quartz and mica in 

 the ftratified ftructure of a fchiftus. 



Now, though in comparing the common ftellften, or quartzy 

 micaceous ftrata of the Alpine countries, with this Brazilian 

 (lone, the one may be faid to be flexible and the other inflexi- 

 ble, this is but faying that the one of thefe is not fenfibly flexi- 

 ble, as is the other. But how many degrees of flexibility may 

 actually take place between that which may be fenfible to com- 

 mon obfervation, and that at which flexibility mud ceafe ? 



Therefore, in feeing the principle upon which the Brazi- 

 lian ftone poflefTes its flexibility, we may underftand the qua- 

 lity of the ftellftein which renders it fo proper for the conftruc- 

 tion of furnaces ; and, converfely, in underflanding the ftruc- 

 ture of the ftellften, we may fee the principle upon which 

 the Brazilian foflil poflefTes flexibility in fo eminent a degree. 



But it would appear, that this is not the only fpecies of ftone 

 which may have this remarkable degree of flexibility. M. le 

 Baron de Dietrich obferves, that the marble tables, preferved 

 in the Borghefe Palace at Rome, under the name of Pietra ela- 

 Jiica, feem to have the fame property. Now, M. Ferber 

 found, that thofe tables were of a true antique white marble, 

 the grains of which have but little cohefion ; and the P. Ja- 

 quier obferved, among the grains of the marble, particles 

 of talc. But among the Alpine ftrata, we find both thofe that 

 are compofed of granulated quartz and mica, and thofe that 

 are compofed of granulated calcareous fpar and mica, fo much 

 refembling each other, that, without trying their hardnefs or 

 their folubility in acids, it would be difficult to diftinguifh 



therm 



