VARIOUS. 197 



In his interesting account of the extinct vol- 

 cano of Beaulieu, in the south of France, he thus 

 Describes a singular stone, which was supposed 

 ;o be transilient, or passing from limestone to 

 lint. It probably rather belongs to the Diamic- 

 ,onic; but the remarks of Saussure rather place 

 t in this division. 



" The upper beds of that rock appear to me 

 calcareous, compact ; but the lower, .or those 

 which approach nearest to the supposed orifice 

 of the crater, are of a substance that has been 

 confounded with petrosilex, but whose essen- 

 tial characters differ from it. I call it silici-calx> 

 because it is composed of silex mixed with cal- 

 careous earth. 



< c It is of a white colour, which, in some spe- 

 cimens, inclines to a grey, in others to a red. 

 Its fracture is perfectly conchoidal and smooth, 

 but without lustre, and of a fine paste. It can- 

 not be called scaly, although in some places 

 there are large scales. Its fragments are sharp, 

 and translucent on the edges. It is a little more 

 than semi-hard, only being capable of being 

 scratched with the point of a knife, and yielding, 

 though rarely, some sparks with steel. 



Cf It makes a weak and Jong effervescence 

 with acids ; it then loses a great part of its hard- 

 ness, but however not so much as to become 



