Vicentine, and Veronese Territories. 19 
basalt and limestone within a vertical depth of about 25 feet. 
The lowest, which forms the base of the mountain, is of lime- 
stone; the upper, constituting its summit, of basaltic peperino. 
The inner layers of basalt are of very little thickness, and may 
perhaps have been injected forcibly between strata of lime- 
stone, rather than the result of successive depositions. At the 
lines of contact both substances are intimately united by a par- 
tial intermixture of basaltic and calcareous particles. The 
basalt is occasionally hard and compact, sometimes highly 
porous, and of an earthy texture, approaching to wacke, and 
passing into a calcareous peperino; qualities which it appa- 
rently owes to the peculiar circumstances that accompanied 
its deposition. The same characters accompany all the trap- 
rocks of the Vicentine and Veronese, which vary at intervals 
from a basaltic breccia to a peperino, a wacke, and a dense 
crystalline and columnar basalt. All of these in turn contain 
amygdaloidal nodules of calcareous spar, chalcedony, semi- 
opal, mesotype, stilbite, analcime, and green earth. 
But the most interesting point of the whole zone on which 
this rock shews itself, is the Purga di Bolca, so celebrated for 
the numerous fossil, fish, and alge, contained between the 
lamine of its bituminous limestone. 
Two facts struck me, on visiting this spot, as not having yet, 
as far as I am aware, attracted the attention they are entitled 
to:—1. That the bituminous and fissile limestone of the Pes-_ 
chiera, or fish-quarry of Bolca, is merely a local variety of the 
horizontal mountain limestone, which constitutes the whole 
semicircular chain of mountains surrounding the Venetian plain. 
2. That it obviously owes its peculiar characters to the effects 
of a volcanic eruption, bursting through the bottom of the 
ocean by which this limestone formation was deposited. 
The two points on which alone fish are ever found, occur on 
the opposite flanks of a ragged and narrow ravine, and, in all 
probability, originally formed but one rock. Both are sur- 
inounted by a massive bed of peperino, traversed by huge 
veins of columnar basalt; and itis only immediately beneath 
this that the fish are found. Ata very short depth below the 
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