ion: Fig. 90.

Temple of Serapis at its period of greatest depression.

_a b_, Ancient mosaic pavement.
_c c_, Dark marine incrustation.
_d d_, First filling up, shower of ashes.
_e e_, Freshwater calcareous deposit.
_f f_, Second filling up.
_A_, Stadium.

]

We have already seen (p. 512) that a temple of Serapis existed long
before the Christian era. The change of level just mentioned must have
taken place some time before the end of the second century, for
inscriptions have been found in the temple, from which we learn that
Septimius Severus adorned its walls with precious marbles, between the
years 194 and 211 of our era, and the emperor Alexander Severus
displayed the like munificence between the years 222 and 235.[720] From
that era there is an entire dearth of historical information for a
period of more than twelve centuries, except the significant fact that
Alaric and his Goths sacked Puzzuoli in 456, and that Genseric did the
like in 545, A. D. Yet we have fortunately a series of natural archives
self-registered during the dark ages, by which many events which
occurred in and about the temple are revealed to us. These natural
records consist partly of deposits, which envelop the pillars below the
zone of lithodomous perforations, and partly of those which surround the
outer walls of the temple. Mr. Babbage, after a minute examination of
these, has shown (see p. 507, note) that incrustations on the walls of
the exterior chambers and on the floor of the building demonstrate that
the pavement did not sink down suddenly, but was depressed by a gradual
movement. The sea first entered the court or atrium and mingled its
waters partially with those of the hot spring. From this brackish medium
a dark calcareous precipitate (_c c_, fig. 90) was thrown down, which
became, in the course of time, more than two feet thick, including some
serpulae in it. The presence of these annelids teaches us that the water
was salt or brackish. After this period the temple was filled up with an
irregular mass of volcanic tuff (_d d_, fig. 90), probably derived from
an eruption of the neighboring crater of the Solfatara, to the height of
from five to nine feet above the pavement. Over this again a purely
freshwater deposit of carbonate of lime (_e e_, fig. 90) accumulated
with an _uneven_ bottom since it necessarily accommodated itself to the
irregular outline of the upper surface of the volcanic shower before
thrown