ely over three well-defined physical zones: the
lowest, or fertile zone, comprising the tract around the skirts of the
mountain up to a level of about 2500 feet, being well cultivated and
covered by dwellings surrounded by olive groves, fields, vineyards, and
fruit-trees; the second, or forest zone, extending to a level of about
6270 feet, clothed with chestnut, oak, beech, and cork trees, giving
place to pines; and the third, extending to the summit and called "the
desert region," a waste of black lava and scoriae with mighty crags and
precipices, terminating in a snow-clad tableland, from which rises the
central cone, 1100 feet high, emitting continually steam and sulphurous
vapours, and in the course of almost every century sending forth streams
of molten lava.

The forest zone is remarkable for the great number of minor craters
which rise up from the midst of the foliage, and are themselves clothed
with trees. Sartorius von Waltershausen has laid down on his map of Etna
about 200 of these cones and craters, some of which, like those of
Auvergne, have been broken down on one side. Many of these volcanoes of
second or third magnitude lie outside the forest zone, both above and
below it; such as the double hill of Monti Rossi, near Nicolosi, formed
in 1659, which is 450 feet in height, and two miles in circumference at
its base. Sir C. Lyell observes that these minor crater-cones present us
with one of the most delightful and characteristic scenes in Europe.
They occur of every variety of height and size, and are arranged in
picturesque groups. However uniform they may appear when seen from the
sea or the plains below, nothing can be more diversified than their
shape when we look from above into their ruptured craters. The cones
situated in the higher parts of the forest zone are chiefly clothed with
lofty pines; while those at a lower elevation are adorned with
chestnuts, oaks, and beech trees. These cones have from time to time
been buried amidst fresh lava-streams descending from the great crater,
and thus often become obliterated.

[Illustration: Fig. 10.--Ideal Section through Etna. (After Lyell.)--A.
Axis of present cone of eruption; B. Axis of extinct cone of eruption;
_a._ Older lavas, chiefly trachytic; _b._ Newer lavas, erupted (with
_a_) before origin of the Val del Bove; _c._ Scoria and lava of recent
age; T. Tertiary strata forming the foundation to the volcanic rocks.
The position of the Val del Bove bef