example, there
is reason for believing that the first result of the renewed energy of
Vesuvius was to blow into the air the upper surface of the mountain.
Again, so late as 1822, during a violent earthquake in Java, a country
which has been repeatedly devastated by earthquakes and volcanic
eruptions, the mountain of Galongoon, which was covered by a dense
forest, and situated in a fertile and thickly-peopled region, and had
never within the period of tradition been in activity, was thus ruptured
by internal forces. In the month of July 1822, after a terrible
earthquake, an explosion was heard, and immense columns of boiling
water, mixed with mud and stones, were projected from the mountain like
a water-spout, and in falling filled up the valleys, and covered the
country with a thick deposit for many miles, burying villages and their
inhabitants. During a subsequent eruption great blocks of basalt were
thrown to a distance of seven miles; the result of all being that an
enormous semicircular gulf was formed between the summit and the plain,
bounded by steep cliffs, and bearing considerable resemblance to the Val
del Bove. Other examples of the power of volcanic explosions might be
cited; but the above are sufficient to show that great hollows may thus
be formed either on the summits or flanks of volcanic mountains. Chasms
may also be formed by the falling in of the solidified crust, owing to
the extrusion of molten matter from some neighbouring vent of eruption;
and it is conceivable that by one or other of these processes the vast
chasm of the Val del Bove on the flanks of Etna may have been produced.

(_c._) _The Physical History of Etna._--The physical history of Etna
seems to be somewhat as follows:--

_First Stage._--Somewhere towards the close of the Tertiary
period--perhaps early Pliocene or late Miocene--a vent of eruption
opened on the floor of the Mediterranean Sea, from which sheets of lava
were poured forth, and ashes mingled with clays and sands, brought down
from the neighbouring lands, were strewn over the sea-bed. During a
pause in volcanic activity, beds of limestone with marine shells were
deposited.

_Second Stage._--This sea-bed was gradually upraised into the air, while
fresh sheets of lava and other _ejecta_ were accumulated round the vents
of eruption, of which there were two principal ones--the older under the
present Val del Bove, the newer under the summit of the principal cone.
Thus was the