516 DOMAIN XII. VOLCANIC. 



also presents granite, evidently affected by heat, 

 the felspar having become dull and shattered*. 

 Several altered rocks are found in volcanic re- 

 gions j and even the lavas sometimes become 

 white, by the action of sulphuric vapoursf . 



HYPONOME I. LIMESTONE. 



This substance deserves the first place, as that 

 ejected by Vesuvius is not only more frequent in 

 cabinets than any other exploded rock, but con- 

 parasitic tains several remarkable parasitic stones : such as 



stones. 



1. The Vesuman of Werner, and idocrase of 

 Hauy, the jacint of Vesuvius according to Saus- 

 sure, the colour resembling that of a pale jacint- 

 It is also found of an olive green, whence it is 

 sometimes called chrysolite by the Neapolitan la- 

 pidaries. It would seem that the latter is, how- 

 ever, the same with the olivine of Werner, also 

 called volcanic chrysolite^. 2. The sommite of 



* It is surprising that the French writers continue to spell d'Or as 

 if it were the golden mountain, while Le Grand (Voyage d'Au- 

 Tergne ii. 66.) has demonstrated, that the name was taken from the 

 river Dor, which, with the Dogne, forms the Dordogne. 



f The lava decomposes into clay, or rather the argil displays it- 

 self; whence the environs of volcanos are very fertile. 



J Because the olivine is found in basalt, the Wernerians reject 

 it from the volcanic substances, while it is in fact the common vol- 

 canic chrysolite, as Breislak has shewn. Gioeni, p. 217, observes, 

 that many scoriae of Vesuvius and Etna contain a yellowish substance 

 like glass, perfectly resembling that in the native iron of Siberia. 



