Dr. Daubeny on the Geology of Sicily. 237 
\t is probable that the latter constitutes the softest variety 
of the Palermo limestone, and that the hardest may be seen in 
the marble of Castronuovo, employed in the columns of the 
Palace at Caserta, near Naples, and in the great staircase of 
the Convent of San Martino near Palermo. 
The formation in general is, however, best marked by the 
beds of chert, with which it is accompanied ; these occur at 
Monti Giuliano near 'Lrepani;* at Termini,,and in some of 
the hills near Palermo,—others, as the Monte Pelegrino, being 
entirely destitute of them. 
The chert presents several beautiful varieties, as will be 
understood, when I remark that the Sicilian jaspers and 
agates are derived either directly from thence, or indirectly 
from the rolled masses in the valleys, or on the sea-shore, 
which this rock appears to have exclusively furnished. 
These beds have sometimes a brecciated or a conglome- 
rated structure, whilst at others, the siliceous matter com- 
bined with a portion of alumine, and just enough of lime to 
cause a feeble action with an acid, forms stripes diverging in 
all directions, the interstices of which are filled up with a 
somewhat lighter coloured and softer variety of the same 
material, 
The jaspideous beds are either red or yellow, the two va- 
rieties often occur together, and are penetrated by veins of 
pure crystalline quartz, thus constituting those beautiful 
agates for which Sicily has so long been celebrated. 
This formation is also marked by the occurrence in it of a 
pulverulent white earth, which, by analysis, is found to con- 
tain half its weight of magnesia. In this, and in the charac- 
ter of phosphorescing vividly on live coals, it resembles the 
pulverulent beds which I observed in the magnesian lime- 
stone near Buda, and which Beudant has already noticed. 
In Hungary, this powdery substance is accompanied with, 
and perhaps derived from, beds of a magnesian limestone, 
with a harsh gritty feel, which, when exposed to the weather, 
* Formerly Mount Eryre, famous for the Temple of Venus. It is one 
of the loftiest mountains of Neptunian origin. Its height is stated by 
Ferrara at about 590 toises, 3540 feet above the sea. 
“} The agates of Sicily were much prized, even among the ancients; 
indeed, it is well known that this stone acquired its name from Achates, 
2 river in Sicily. 
