Dr Daubeny on the Geology of Sicily. 115 
the hills near Palermo, — others, as the Monte Pelegrino, being 
entirely destitute of them. 
The chert presents several beautiful varieties, as will be un- 
derstood, 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 ap- 
pears to have exclusively furnished. 
These beds have sometimes a brecciated or a conglomerated 
structure, whilst at others the siliceous matter combined 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 inter- 
stices of which are filled up with a soiiiewhat lighter coloured 
and softer variety of the same material. 
The jaspideous beds are either red or yellow, the two varie- 
ties 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 character 
of phosphorescing vividly on live coals, it resembles the pulve- 
rulent beds which I observed in the magnesian limestone near 
Buda, and which Beudant has already noticed. In Hungary, 
this powdery substance is accompanied with, and perhaps deri- 
ved from, beds of a magnesian limestone, with a harsh gritty 
feel, which, when exposed to the weather, decompose into rhom- 
boidal fragments. Near Palermo there are beds of a siliceous 
limestone, containing a good deal of magnesia, which decompose 
much in the same manner. The pulverulent Palermo limestone 
was in great request formerly as a remedy for various disorders, 
and large quantities of it, under the name of the Earth of Baida, 
used to be exported or sold for domestic consumption : at pre- 
sent it is rarely to be met with in the shops, although it may 
have been useful as an antacid, for the same purposes for which 
we employ magnesia, and, therefore, perhaps has better preten- 
sions to repute than many substances that still maintain their 
place in pharmacy. 
* The agates of Sicily were much prized, even among the ancients; indeed, it 
Is well known that this stone acquired its name from Achates, a river in Sicily. 
H 2 
