238 Dr. Daubeny on the Geology of Sicily. 
decompose into rhomboidal fragments. Near Palermo 
there are beds of a siliceous limestone, containing a good 
deal of magnesia, which decompose much in the same man- 
ner. The pulveruleni Palermo limestone was in great re- 
quest formerly, as a remedy for various disorders, and large 
quantities of it, under the name of the Earth of Biada, used 
to be exported or sold for domestic consumption: at present 
itis rarely to be met with in the shops, although it may have 
been useful as an antacid, for the same purpose fors which we 
employ magnesia, and, therefore, perhaps has better preten- 
sions to repute than many substances that still maintain their 
place in pharmacy. 
Before I quit the subject of the Palermo limestone, I must 
not omit a circumstance relative to the rock of Mount Pelegri- 
no, near that city, which seems to deserve notice. Notwith- 
standing the uniform compactness of this stone, wherever it 
has been recently quarried, we find it in those parts which 
have been exposed to the weather, honeycombed in an extra- 
ordinary degree, by holes of considerable size, which pene- 
trate several inches below the surface, but indicate, from the 
gradual decrease of their dimensions, that the cavities were 
formed by the action of the weather, sinking gradually into 
the substance of the stone. 
These cavities, in their size and appearance, reminded me 
of those which occur near the surface ofa hard siliceous lime- 
stone, belonging to the Oolite formation, found near Cirences- 
ter in Gloucestershire, which has obtained the local name of 
the Dagham alum-stone. 
This irregular disintegration of the surface is common, in a 
greater or less degree, to most limestones exposed to the 
weather; but it would be interesting to discover, whether 
the greater size of the cavities formed in these two instances, 
be derived from any peculiarity in the nature of the rock itself 
or in the circumstance under which it has been placed. — 
With regard to the age of the Palermo limestone, I cannot 
speak with confidence, but I conceive, that the facts already 
stated, warrant me in considering it, for the present, as cor- 
responding to the Zechstein of the Germans, and the Mag- 
nesian limestone of England; in corroboration of which, I 
may perhaps add, that most of the specimens contain mag- 
nesia, although not generally in very large proportion. 
All the high ground near Palermo is occupied by this an- 
cient calcareous formation, but the valleys and coast are 
