342 : Dr. Daubeny on the Geology of Sicily. 
ot us now consider the characters of the subjacent stra- 
‘tum, which, in point of extent, is by far the most considera- 
ble-in Sicily. Indeed, it might be safely said, that nearly half 
the surface of the island is constituted of this and the subordi-: 
nate beds,.as it extends from the neighbourhood of Palermo 
and Termini on the north, to Terra Nuovo on the south, oc- 
cupies nearly the whole ‘of the centre, and extends on the 
east to the skirts of Etna, The predominating rock in this 
formation is-a bluish plastic clay, with which are-associated 
heds of gypsum, of blue limestone, of a dark-brown slaty 
marl, of a white argillaceous limestone frequently alternatin 
with marl, and of a brecciated calcareous rock, with ova 
masses ofa white compact limestone, like that which occurs 
in the Palermo rock. 
e blue clay. rarely contains shells, and the ‘only ones I 
Sent sbed in a state sufficiently distinct to be made out, 
were a Mmytilus.and a cardium. — | never recollect to have seen 
it resting on any of the other beds which I have mentioned 
us being associated with it; in every instance it appeared to 
be the fundamental rock. 
The beds of gypsum found incumbent upon it rank among 
the most gipking | ELSE the geology. of Sicily. They 
are composed som ypsum, sometimes of entire 
ease selenite, which Secu a confused crystallization. 
Plates may sometimes be detached nearly a foot in length, 
and six ip eight inches in breadth.* 
The sulphate. of lime occurs also dispersed in, crystals 
through a white clay, and in cavities of the blue clay, 
companied with those crystallizations of sulphate of strontian 
and of native sulphur, for which Sicily has long been cele- 
brated, 
It would. appear that beds of sulphur are found every- 
whepe’ disscntinated through the substance of this blue clay 
formation,f for though Sicily has long supplied all Eajope 
shad that mineral, its stores are as yet very far from. being 
cx ted. 
* The arrow-headed variety of crystals seemed the moat sre 
{ As ior i instance, in that of Radehaoy, near Crapina, i 
where the sulphur is met with ti in balls disseminated thro peed clay, and 
covered with marl, containing impressions of fishes, &c, the whole a 
ing on the plastic clay. 
its 
