24* A SYSTEM OF 



e. Dark grey, with white grains of feltfpat 

 alio, from Guftavsftrom. 



Many varieties of this kind, in regard 

 to colour, are found in form of nodules or 

 loofe flones in Sweden ; but I have only 

 meniioned the hardeft and fineft of thofe 

 which are found in the rocks •, becaufe, 

 beficles thefe, there are coarfe porphy- 

 ries found, which fcarce admit of any 

 poliih. The dark red porphyry has been 

 mofc employed for ornaments in build- 

 ing : yet it is not the only one known by 

 the name of Pcrfido, the Italians apply- 

 ing the fame name alio to the black 

 kind f 



SECT. CCLXVII. 



G. The Trapp of the Swedes. Saxum compofi- 

 tum jafpide martiali mollis feu argilla mar- 



tiali induratd, et 



This kind of ftone fometimes conftitutes 

 or forms whole mountains-, as, for example, 

 the mountain called Hunneberg, in the 

 province of Weftergcttland, and at Dram- 

 men in Norway; but it is ofcncr found in 

 form of veins in mountains of another 

 kind, running commonly in a ferpentine 

 manner, contrary or acrofs to the direction 

 of the rock itfelf. It is not homogeneous, 

 as may be plainly feen at thole places 

 where it is not pre/Ted clafe together ; but 

 where it is preficd clofe, it feems to be 

 perfectly free from heterogeneous iiib- 

 fcances. When this kind is very coarfe, it 

 is rnterfperled with feltfpat \ but it is net 

 known if the finer forts likewife contain 



any 



