ince it is
composed of regular sedimentary deposits, containing marine shells, its
position proves that, subsequently to its formation, there has been a
change of more than twenty feet in the relative level of land and sea.

[Illustration: Fig. 87.

_a_, Antiquities on hill S. E. of Puzzuoli (see ground plan, fig. 86).

_b_, Ancient cliff now inland.

_c_, Terrace composed of recent submarine deposit.]

The sea encroaches on these new incoherent strata; and as the soil is
valuable, a wall has been built for its protection; but when I visited
the spot in 1828, the waves had swept away part of this rampart, and
exposed to view a regular series of strata of tuff, more or less
argillaceous, alternating with beds of pumice and lapilli, and
containing great abundance of marine shells, of species now common on
this coast, and amongst them _Cardium rusticum_, _Ostrea edulis_, _Donax
trunculus_, Lamk., and others. The strata vary from about a foot to a
foot and a half in thickness, and one of them contains abundantly
remains of works of art, tiles, squares of mosaic pavement of different
colors, and small sculptured ornaments, perfectly uninjured.
Intermixed with these I collected some teeth of the pig and ox. These
fragments of building occur below as well as above strata containing
marine shells. Puzzuoli itself stands chiefly on a promontory of the
older tufaceous formation, which cuts off the new deposit, although I
detected a small patch of the latter in a garden under the town.

[Illustration: Fig. 88.

VIEW OF BAY OF BAIAE.

1. Puzzuoli. 2. Temple of Serapis. 3. Caligula's Bridge
4. Monte Barbaro. 5. Monte Nuovo. 6. Baths of Nero. 7. Baiae.
8. Castle of Baiae. 9. Bauli. 10. Cape Misenum. 11. Mount Epomeo in
Ischia. 12. South Part of Ischia.

]

From the town the ruins of a mole, called Caligula's Bridge, run out
into the sea (see fig. 88, p. 509).[713] This mole, which is believed to
be eighteen centuries old, consists of a number of piers and arches,
thirteen of which are now standing, and two others appear to have been
overthrown. Mr. Babbage found, on the sixth pier, perforations of
lithodomi four feet above the level of the sea; and, near the
termination of the mole on the last pier but one, marks of the same, ten
feet above the level of the sea, together with great numbers of balani
and flustra. The depth of the sea, at a very small distance from most of
the piers, is from thirty to fifty feet.