III. Of the Flexibility of the Brazilian Stone. By 

 James Hutton, M. D. F. R. S. Edin. and Member of 

 the Royal Academy of Agriculture at Paris. 



{Read Feb. 7. 1791.] 



NO quality is more inconliftent with the character of a ftone 

 than flexibility. A flexible (tone, therefore, prefents an 

 idea which naturally ftrikes us with furprife. For though 

 among mineral bodies, we find flexible fubftances of the ftony 

 kind, fuch as mica, mountain leather, and amianthus, thefe 

 minerals owe their flexibility, either to their thinnefs, or to the 

 fibrous ftruclure of their parts. Therefore, when a ftone of 

 any considerable thicknefs is faid to have flexibility, we are led 

 to think that here is fomething very extraordinary ; and we wi£h 

 to know upon what depends that quality, nowife proper to a 



ftone. 



Such, however, is the ftone from Brazil, of which the Baron 

 de Dietrich read a defcription in the Royal Academy of 

 Sciences, in January 1784. There is alfo at prefent, in the pof- 

 feflion of Lord Gardenston, a fpecimen of ftone, which 

 correfponds with that defcription, inferted in the Journal de 

 Phyfique for the year 1784*. The length of the ftone which I 

 have examined is twelve inches, the breadth about five, and 

 the thicknefs half an inch. When this ftone is fupported by 



. the 



* Tom. xxiv. p. 275, 276. 



