roughout all the eruptions of modern
times the northern side of the mountain, that is the old crater and
flank of Somma, has been secure from the lava-flows, and has enjoyed an
immunity which does not belong to the southern and western side. If we
look at a map of the mountain showing the direction of the streams
during the last three centuries,[13] we observe that all the streams of
that period flowed down on the side overlooking the Bay of Naples; on
the opposite side the wall of Monte di Somma presents an unbroken front
to the lava-streams. From this it may be inferred that one side, the
west, is weaker than the other; and consequently, when the lava and
vapours are being forced upwards, under enormous pressure from beneath,
the western side gives way under the strain, as in the case of the
fissure of 1872, and the lava and vapours find means of escape. From
what has happened in the past it is clear that no place on the western
side of the mountain is entirely safe from devastation by floods of
lava; while the prevalent winds tend to carry the ashes and lapilli,
which are hurled into the air, in the same westerly direction.

[1] For an excellent view of this remarkable volcanic group see Judd's
_Volcanoes_, 4th edition, p. 43.

[2] Plutarch, _Life of Cassius_; _ed. Reiske_, vol. iii. p. 240.

[3] Strabo gives the following account of the appearance and condition
of Vesuvius in his day:--"Supra haec loca situs est Vesuvius mons, agris
cinctus optimis; dempto vertice, qui magna sui parte planus, totus
sterilis est, adspectu sinereus, cavernasque ostendens fistularum plenas
et lapidum colore fuliginoso, utpote ab igni exesorum. Ut conjectarum
facere possis, ista loca quondam arsisse et crateras ignis habuisse,
deinde materia deficiente restricta fuisse."--_Rer. Geog._, lib. v.

[4] A tablet over the entrance records this act of pious liberality, and
is given by Phillips, _loc. cit._, p. 12.

[5] The stone pine, _Pinus pinea_, which Turner knew how to use with so
much effect in his Italian landscapes.

[6] Bulwer Lytton's _Last Days of Pompeii_ presents to the reader a
graphic picture of the terrible event here referred to:--"The eyes of
the crowd followed the gesture of the Egyptian, and beheld with
ineffable dismay a vast vapour shooting from the summit of Vesuvius, in
the form of a gigantic pine tree; the trunk--blackness, the
branches--fire! A fire that shifted and wavered in its hues with every
moment--now fie