ned isolated masses has been much
diminished by the elevation of their base, caused by these currents.
They may, perhaps, be the remnants of lateral cones which existed before
the Val del Bove was formed, and may hereafter be once more buried by
the lavas that are now accumulating in the valley.

[Illustration: Fig. 51.

View of the rocks Finochio, Capra, and Musara, Val del Bove.]

From no point of view are the dikes more conspicuous than from the
summit of the highest cone of Etna; a view of some of them is given in
the annexed drawing. (Fig. 52.)

_Eruption of 1811._--I have alluded to the streams of lava which were
poured forth in 1811 and 1819. Gemmellaro, who witnessed these
eruptions, informs us that the great crater in 1811 first testified by
its loud detonations that a column of lava had ascended to near the
summit of the mountain. A violent shock was then felt, and a stream
broke out from the side of the cone, at no great distance from its apex.
Shortly after this had ceased to flow, a second stream burst forth at
another opening, considerably below the first; then a third still lower,
and so on till seven different issues had been thus successively formed,
all lying upon the same straight line. It has been supposed that this
line was a perpendicular rent in the internal framework of the mountain,
which rent was probably not produced at one shock, but prolonged
successively downwards, by the lateral pressure and intense heat of the
internal column of lava, as it subsided by gradual discharge through
each vent.[568]

_Eruption of 1819._--In 1819 three large mouths or caverns opened very
near those which were formed in the eruptions of 1811, from which
flames, red-hot cinders, and sand were thrown up with loud explosions. A
few minutes afterwards another mouth opened below, from which flames
and smoke issued; and finally a fifth, lower still, whence a torrent of
lava flowed, which spread itself with great velocity over the deep and
broad valley called "Val del Bove." This stream flowed two miles in the
first twenty-four hours, and nearly as far in the succeeding day and
night. The three original mouths at length united into one large crater,
and sent forth lava, as did the inferior apertures, so that an enormous
torrent poured down the "Val del Bove." When it arrived at a vast and
almost perpendicular precipice, at the head of the Valley of Calanna, it
poured over in a cascade, and, being hardened in its de