on effected by heat on the edges of the horizontal
beds, in contact with the vertical and more crystalline mass. On the
side of Mompiliere, one of the towns overflowed in the great eruption
above described, an excavation was made in 1704; and by immense labor
the workmen reached, at the depth of thirty-five feet, the gate of the
principal church, where there were three statues, held in high
veneration. One of these, together with a bell, some money, and other
articles, were extracted in a good state of preservation from beneath a
great arch formed by the lava. It seems very extraordinary that any
works of art, not encased with tuff, like those in Herculaneum, should
have escaped fusion in hollow spaces left open in this lava-current,
which was so hot at Catania eight years after it entered the town, that
it was impossible to hold the hand in some of the crevices.

_Subterranean caverns on Etna._--Mention was made of the entrance of a
lava-stream into a subterranean grotto, whereby the foundations of a
hill were partially undermined. Such underground passages are among the
most curious features on Etna, and appear to have been produced by the
hardening of the lava, during the escape of great volumes of elastic
fluids, which are often discharged for many days in succession, after
the crisis of the eruption is over. Near Nicolosi, not far from Monti
Rossi, one of these great openings may be seen, called the Fossa della
Palomba, 625 feet in circumference at its mouth, and seventy-eight deep.
After reaching the bottom of this, we enter another dark cavity, and
then others in succession, sometimes descending precipices by means of
ladders. At length the vaults terminate in a great gallery ninety feet
long, and from fifteen to fifty broad, beyond which there is still a
passage, never yet explored; so that the extent of these caverns remains
unknown.[566] The walls and roofs of these great vaults are composed of
rough and bristling scoriae, of the most fantastic forms.

_Marine strata at base of Etna._--If we skirt the fertile region at the
base of Etna on its southern and eastern sides, we behold marine strata
of clay sand, and volcanic tuff, cropping out from beneath the modern
lavas. The marine fossil shells occurring in these strata are all of
them, or nearly all, identical with species now inhabiting the
Mediterranean; and as they appear at the height of from 600 to 800 feet
above the sea near Catania, they clearly prove t