Dr Daubeny on the Geology of Sicily. 367 
gradation, dependent on the relative antiquity of the beds, down 
to the lavas of the present period, which have the usual cellu- 
lar and vitreous aspect of such products. 
Having made this observation, whilst in Sicily, I was pleased, 
on my return, to find, on perusing some papers of the celebrated 
Prussian geologist Von Buch (in the Transactions of the Ber- 
lin Academy), that a similar observation is there recorded, on 
lavas in general, which are conceived by him to owe their pecu- 
liar characters to an admixture of trachyte with .iitaniferous 
iron. 
It would be inconsistent, however, with the limits of this com- 
munication, to pursue the subject farther, as all general infe- 
rences, with regard to this class of substances, would find a more 
natural place in an essay on the Ph sen omen a of Volcanoes in 
general. 
To conclude, then, it would appear that the Island of Sicily 
contains rocks of the primitive, transition, secondary and tertiary 
classes. 
The primitive are only found at the north-east corner of the 
island, near Messina, where the prevailing rock appears to be 
gneiss. 
The transition constitute a chain of hills, extending obliquely 
from Melazzo on the north coast, to Taormina on the west. 
They consist chiefly of mica-slate and clay-slate, quartz-rock, 
grey-wacke, sandstone and limestone. 
The secondary rocks are found chiefly in a line parallel with 
the north coast. They consist, 1st, Of red sandstone, with beds 
of shale, extending from Cape Orlando to Cape Cefalu. 3c%, 
Of a compact limestone, with beds of chert, jasper and agate, 
which constitutes the Madonia Mountains, and extends from 
Cefalu to Palermo, and from thence to Trepani. It, perhaps, 
corresponds with the magnesian limestone of England. The 
tertiary rocks consist either of beds of blue clay and marl, 
containing much gypsum and selenite, sulphur, sulphate of 
strontian, alum, and common salt. 3 dly, Of a calcareous brec- 
cia, replete with shells of a recent date, which is seen exten- 
sively on the western coast, at the level of the sea ; and as we 
trace it south, is found to rest on the blue clay ; or, 4 thly. Of 
beds of shelly limestone, which occupy all the south of the 
island, and alternate repeatedly with beds of volcanic matter. 
