The BRAZILIAN STONE... © 94 
operations of heat and cold, or the effects of frequent expan- 
fions and contra¢tions, partially applied. Now, it is precifely 
the fame ftru€ture which is required for thofe two purpofes, 
that of procuring flexibility, and that of refifting fra€ture by 
the partial application of heat and cold; and the two things 
here compared, the ftellften and the Brazilian ftone, are of the 
fame conftruction, fo far as compofed of quartz and mica in 
the ftratified ftruéture of a {chiftus. 
Now, though in comparing the common ftellften, or quartzy 
-micaceous ftrata of the Alpine countries, with this Brazilian 
ftone, 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 muft ceafe ? 
THEREFORE, in feeing the principle upon which the Brazi- 
lian ftone poffeffes 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 underftanding the ftruc- 
ture of the ftellften, we may fee the principle upon which 
the Brazilian foffil poffeffes 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 DieTricu obferves, that the marble tables, preferved 
in the Borghefé Palace at Rome, under the name of Pietra ela- 
Jlica, feem to have the fame property. Now, M. Ferser 
found, that thofe tables were of a true antique white marble, 
the grains of which have but little cohefion ; and the P. Ja- 
quizR 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 {par and. mica, fo much 
refembling each other, that, without trying their hardnefs or 
their folubility i in acids, it would be difficult to diftinguifh 
; them. 
