Dr Daubeny on the Geology of Sicily. 857 
It is not long since the proprietor of some land in the interior 
congratulated himself on his good fortune, in being able to col- 
lect a large supply of sulphur already purified, by merely 
placing vessels to receive a stream of that substance, which was 
constantly issuing from the side of a hill. This was occasioned 
by a bed of sulphur in the interior of the mountain having 
caught fire, and the heat generated by the combustion of one 
portion serving to melt the remainder ; Nature having, in this 
instance, adopted the wasteful process employed from time im- 
memorial by the Sicilians, for getting rid of the intermixed clay, 
which consists simply in collecting the materials in large heaps, 
and setting fire to them on the surface, thus causing the lique- 
faction of one portion by the combustion of another. 
At Macaluba, a hill near Girgenti, consisting of blue clay, 
there is a continual disengagement of gas (which I found to 
consist of carbonic acid and carburetted hydrogen) from small 
cavities, shaped like craters, which are filled with muddy water, 
mixed with petroleum. When I visited the spot the action was 
rather feeble; but there are times when the quantity of gas 
emitted is so great, as to throw up the mud to the height of 
800 feet, so as almost to justify the name of an Air-Volcano, 
which has been applied to it. 
I shall mention only one other proof of the same fact, which 
is exhibited near the town of Sciacca, the ancient baths of Seli- 
nus. On the slope of Mount Calogero, the ancient Mons Cro- 
nius, at the back of the above town, are baths of which the tem- 
perature is no less than 180° of Fahrenheit, and which, from 
their sensible qualities, seem to contain sulphate of magnesia 
and sulphuretted hydrogen gas. Like the Harrowgate waters, 
they are much used for cutaneous disorders. At a higher level 
we lose the rocks belonging to the blue clay formation, and find 
ourselves upon a white saccharoid limestone, of a compact nature, 
containing kidney-shaped masses of flint, like those seen in the 
chalk-strata, which continues to the summit of the mountain. 
The age of this limestone I must leave for other travellers to 
ascertain ; for though I should be disposed, from its general 
characters, to refer it to the same formation as that of Monte 
Giuliano, near Trepani, yet the presence in it of nummulites 
would lead one to suspect a more recent origin. 
