DOMAIN VIII. DIAMICTONIC. 37 



cannot with propriety be arranged under 

 either. The celebrated glazed rock, which 

 Saussure observed near the monastery of 

 St. Bernard, is of this description ; and 

 there is a specimen in the author's collec- 

 tion. It has been called an intimate com- 

 bination of quartz and roche de come. 



Most of the Derivative Rocks of Kirwan 

 belong to this Domain. The name and 

 idea he is said to have borrowed from 

 Bergman. The aggregated stones of Kir- 

 wan comprehend granite, gneiss, porphyry, 

 amygdalite, sand-stone, and other sub- 

 stances, visibly compounded of various 

 materials; while his derivative stones he 

 distinguishes from aggregates by this, " that 

 the associated ingredients are not visibly 

 distinct, or at least require microscopes to 

 render them so/" He adds, that a deriva- 

 tive stone may be denominated from the 

 species (that is, the Mode), w r hich still pre- 

 dominates; but if it participate equally of 

 both, it may receive its denomination from 

 either. The siderous, siliceous, and argil- 

 laceous earths, form the most frequent 



