33,1 ON THE FORMATION OF ROCKS. [Ai gus^ 



mains of scoria^ craters^ cinders, &c. &c. but are in 

 vqcattered and detached masses. Here the analogy is 

 not sc direct as in the second order, though nearer it 

 than any of the Neptunian origin. The greatest part 

 of this order is basalt, in detached masses, or long 

 ridges ; occupying in general the tops of small hills, 

 having no resemblance or relation to the surrounding 

 strata ; and covering indiscriminately all the classes 

 of rocks as well as every species of alluvial ; in some 

 places it has even overlaid vegetable mould : in all 

 which characters it agrees with the rocks of recent vol- 

 canoes. In its component parts, and imbedded crys- 

 tals, it is equally resembling, having crystals of pe- 

 ridot, and pyroxine, disseminated in it, like the recent 

 Lavas of Mount Yesuvius. As in the Lavas of recent 

 Volcanoes, so in this order, tiiere arc no metallic veins 

 or deposits found ; which seems to be a characteristic 

 difference drawn between the two origins, that cannot 

 be mistaken) and perhaps would form a line of separa^ 

 tion sufficiently strong of itself without the aid of any 

 other difference. 



Pitclistone) greenstone, pearistone, porphyry, 

 clinkstone, &c. &c. are names given to the different 

 kinds of rocks found in what Werner calls his newest 

 floetz trap class: they indifferently cover all other 

 classes of rocks and alluvial, and as they are general- 

 ly found in the vicinity of basalt, they must be consi- 

 dered of the same origin. This kind of porphyry has 

 a petrosiliceous base, with crystals of feldspar, not the 

 dull fractured porphyry, with crystals of quartz and 

 feldspar, which generally covers the primitive, though it 



