284 



greenish gray, or mountain green, containing 

 long crystals of vitreous feldspar, appears ex- 

 posed. It is the real porphyrschiefer of Werner ; 

 and it would be difficult to distinguish, in a 

 collection of stones, the phonolite of Parapara 

 from that of Bilin in Bohemia. It does not 

 however here form rocks with grotesque shapes* 

 but little hills covered with tabular blocks, large 

 plates extremely sonorous, translucid on the 

 edges, and wounding the hands when broken. 



Such are the successions of rocks, which I 

 described on the spot, as I progressively found 

 them, from the lake of Tacarigua to the entrance 

 of the steppes. Few places in Europe display a 

 geological constitution so well worthy of being 

 studied. We saw there in succession six for- 

 mations : 



mica-slate gneiss ; 

 green slate (transition) ; 

 black limestone (transition) ; 

 serpentine and gruenstein ; 

 amygdaloid (with pyroxene) ; and 

 phonolite. 



I must observe in the first place, that the sub- 

 stance, which we have just described under the 

 name of gruenstein, in every respect resembles 

 that, which forms layers in the mica-slate of 

 Cape Blanc, and veins near Garaccas # . It dif- 



* See above, vol. iii, p. 405 ; and p. 59 of the present 

 volume. 



