Etna), until it meets the first line
at Catania, the lines, will be found to enclose an angle of 26 deg.. If we
adopt the same plan with Gemellaro's map, the included angle is found to
be 53 deg., and in the case of the maps of Ferrara and Recupero more than
60 deg.. Again, it has been stated on good authority, that the lava of 396
B.C. which enters the sea at Capo di Schiso flowed for a distance of
nearly 30 miles; the map shows us that its true course was less than 16
miles. Lyell in 1858 gives a section of the mountain from West 20 deg. N.,
to East 20 deg. S., but a comparison with the new map proves that the
section is really taken from West 35 deg. N. to East 35 deg. S., an error which
at a radius of ten miles from the crater would amount to a difference of
nearly three miles.

The mantle of Carlo Gemellaro appears to have fallen upon Cav. Orazio
Silvestri, Professor of Chemistry in the University of Catania. He has
devoted himself with unwearying vigour to the study of the mountain, and
his memoirs have done much to elucidate its past and present history.
His most recent work of importance on the subject is entitled _I
Fenomeni Vulcanici presentati dall'Etna nel 1863-64-65-66_. It was
published in Catania in 1867, and contains an account of some very
elaborate chemico-geological researches.

CHAPTER II.

PHYSICAL FEATURES OF THE MOUNTAIN.

Height.--Radius of Vision from the summit.--Boundaries.--Area.--
Population.--General aspect of Etna.--The Val del Bove.--Minor
Cones.--Caverns.--Position and extent of the three Regions.--Regione
Coltivata.--Regione Selvosa.--Regione Deserta.--Botanical Regions.--
Divisions of Rafinesque-Schmaltz, and of Presl.--Animal life in the
upper Regions.

In the preceding chapter we have discussed the history of Mount Etna;
the references to its phenomena afforded by writers of various periods;
and the present state of the literature of the subject. We have now to
consider the general aspect and physical features of the mountain,
together with the divisions of its surface into distinct regions.

The height of Etna has been often determined. The earlier writers had
very extravagant notions on the subject, and three miles has sometimes
been assigned to it. Brydone, Saussure, Shuckburgh, Irvine, and others,
obtained approximations to the real height; it must be borne in mind,
however, that the cone of a volcano is liable to variations in height at
dif