MODE IV. FELSITE. Yf \ 



blende; yet at the same time it is distinguished 

 from the common species of porphyry, by its gross 

 slaty fracture. But since to the principal mass 

 of this stone the name of Mingstein (sounding- 

 stone) has been given, because its larger plates, 

 when struck, give a sound almost metallic; it 

 seems that the name of klingstein porphyr (kling- 

 stone porphyry) would be more characteristic, and 

 more conformable to analogy. 



" From this short historical account it may 

 sufficiently be seen, what great uncertainty and 

 want of accuracy has even of late prevailed in the 

 geological knowledge of the mountainous part of 

 the globe. For this reason the editor of the ma- 

 gazine for the Natural History of Swisserland has 

 highly merited the thanks of the public, for having 

 occasioned, by means of a prize question, that 

 this intricate subject has been investigated by two 

 learned mineralogists, Karsten and Voigt, and cor- 

 rectly explained in their two papers, crowned with 

 the prize : " On argillaceous schistus, horn-slate, 

 and on wake*." 



" The klings tone-porphyry belongs to that divi- 

 sion of mountains which, by modern geologists, are 



* ' ' Magazin fur die Naturkunde Helvetiens," by Dr. Hopfner. 

 Zurich, 1788. Vol. iii. page 168, seq. 



