we find records of eruptions. It is said also that the philosopher
Empedocles sought fame and death by casting himself into the fiery
crater. There has thus in the case of this mountain been no such long
period of repose as occurred in Vesuvius. Though our records of the
outbreaks are exceedingly imperfect, they serve to show that the vent
has maintained its activity much more continuously than is ordinarily
the case with volcanoes. Ætna is characteristically a lava-yielding
cone; though the amount of dust put forth is large, the ratio of the
fluid rock which flows away from the crater is very much greater than
at Vesuvius. Nearly half the cone, indeed, may be composed of this
material. Our space does not permit anything like a consecutive story
of the Ætnean eruptions since the dawn of history, or even a full
account of its majestic cone; we can only note certain features of a
particularly instructive nature which have been remarked by the many
able men who have studied this structure and the effects of its
outbreak.

The most important feature exhibited by Ætna is the vast size of its
cone. At its apex its height, though variable from the frequent
destruction and rebuilding of the crater walls, may be reckoned as
about eleven thousand feet. The base on which the volcanic material
lies is probably less than a thousand feet above the sea, so that the
maximum thickness of the heap of volcanic ejections is probably about
two miles. The average depth of this coating is probably about five
thousand feet, and, as the cone has an average diameter of about
thirty miles, we may conclude that the cone now contains about a
thousand cubic miles of volcanic materials. Great as is this mass,
it is only a small part of the ejected material which has gone forth
from the vent. All the matter which in its vaporous state went forth
with the eruption, the other gases and vapours thus discharged, have