atter was being erupted from volcanic
vents at various points around, and spread over the sea-bed.

Such is the character of the general floor on which the more recent
crater-cones of this district have been built. These are numerous, and
all extinct with the exception of the Solfatara, near Puzzuoli, from
which gases mixed with aqueous vapour are continually being exhaled. The
gases consist of sulphuretted hydrogen mixed with a minute quantity of
muriatic acid.[1] This district is also remarkable for containing
several lakes occupying the interiors of extinct craters; amongst
others, Lake Avernus, which, owing to its surface having been darkened
by forests, and in consequence of the effluvia arising from its stagnant
waters, has had imparted to it a character of gloom and terror, so that
Homer in the _Odyssey_ makes it the entrance to hell, and describes the
visit of Ulysses to it. Virgil follows in his steps. Another lake of
similar origin is Lake Agnano. Here also is the Grotto del Cane, a
cavern from which are constantly issuing volumes of carbonic acid gas
combined with much aqueous vapour, which is condensed by the coldness of
the external air, thus proving the high temperature of the ground from
which the gaseous vapour issues. This whole volcanic region, so replete
with objects of interest,[2] may be considered, as regards its volcanic
character, in a moribund condition; but that it is still capable of
spasmodic movement is evinced by the origin of Monte Nuovo, the most
recent of the crater-cones of the district. This mountain, rising from
the shore of the Bay of Baiae, was suddenly formed in September 29th,
1538, and rises to a height of 440 feet above the sea-level. It is a
crater-cone, and the depth of the crater has been determined by the
Italian mineralogist Pini to be 421 English feet; its bottom is thus
only 19 feet above the sea-level. A portion of the base of the cone is
considered partly to occupy the site of the Lucrine Lake, which was
itself nothing more than the crater of a pre-existent volcano, and was
almost entirely filled up during the explosion of 1538. Monte Nuovo is
composed of ashes, lapilli, and pumice-stones; and its sudden formation,
heralded by earthquakes, and accompanied by the ejection of volcanic
matter mixed with fire and water, is recorded by Falconi, who vividly
depicts the terror and consternation of the inhabitants of the
surrounding country produced by this sudden and terrible o