322 



ILLUSTRATIONS OF THE 



ever, from further explanations, which M. Pa. 

 trin has fince given, that Dr Hutton was mif, 

 taken in his conjeclure, and that, in Xht pierre 

 graphique of the former mineralogift, the quartz 

 gives its form to the feltfpar, preferving in its 

 cryftals their natural angle of 120 degrees *. It 

 is impoffible, I think, to doubt of the accuracy 

 of this ilatement ; and the graphical (lone of 

 Portfoy muft therefore be admitted to differ 

 materially from that of Daouria. They are not, 

 however, without fome confiderable affinity, be- 

 lides that of their outward appearance ; for, 



generally 

 moulded on the feltfpar, the feltfpar is alfo oc- 



calionally imprefled by the quartz, and feme- 

 times even included in it. They may be con- 

 fidered as varieties of the fame fpecies of gra- 

 iiite ; and the pierre graphiqiie of Corfica is 

 probably a third variety, different from them 

 both. 



that all thefe 





hough the quartz in the former is 



289 



It Vv^ould feem. h 



Hones lead exadly to the fame conclulion. M. Pa- 

 trin defcribes his fpecimen as containing quartz 

 cryftals, that are for the moft part only cafes, ha- 

 ving their interior filled with feltfpar. " Le felt- 



fpath 



A 



* Journal Eritannique (of Geneva), 1798, vol. viw 



I 



Sciences et Arts, p. 78. 



t 



