Parker, John Henry: The archaeology of Rome (1,text): I. The primitive fortifications (Oxford [u.a.], 1874)

2

Modes of Construction.

[chap.

Of this material are part of the agger of Servius Tullius; the great
wall fifty feet high and twelve thick, on the eastern side of the Forum
of Augustus, (with the wall of travertine on the north side of the
Forum Transitorium inserted in it, about a fourth of the height,)
also the wall on the opposite side of the latter forum, on the greater
part of which the backs of the houses are built, but a part has been
cased with marble, and had the fine cornice and detached marble
columns of the Temple of Pallas built up against it.
III. Lapis Gabinus, called sperone ; this resembles the peperino
so much that it is not always easy to distinguish them, but peperino
is harder than sperone. The ancient quarries are at Gabii.
The triple arch at the mouth of the Cloaca Maxima, inserted in
the tufa wall called the Pulchrum Littus—the Arco de Pantano', also
inserted in the great tufa wall of the Kings—the substructure of the
Tabularium,—and the Ponte di Nono—are all of this material. These
two stones resist fire, and were ordered by Nero to be used a.d. 64,
after the great fire in Rome. The Lapis Gabinus is also believed
to have been used originally, before even the peperino.
IV. Lapis Tiburtinus, called travertino or travertine, a limestone,
the ancient quarries of which are between Tibur or Tivoli and Aquae.
Albulae, near the river Anio. The stone was probably floated down
to Rome on rafts. It is white when new, and becomes a warm
yellow. The columns of the temple of the Sibyl—the tomb of
the Plautia family at Tivoli—the tomb of Caecilia Metella—and the
Colosseum, are well-known examples of this stone. It is the stone
generally used in the buildings of the first three centuries of the
Christian era in Rome.
V. Silex, called selce, a basaltic lava resembling iron in colour,
and almost as hard; it gives out sparks when struck with iron k.
Several currents of this lava cross the Campagna, coming from
the crater, now the Lake of Albano, and extending near to Rome :
one reaches as far as the tomb of Cascilia Metella, two miles from
Rome on the Via Appia. It is used for concrete, and pavements.
It was first used for this latter purpose in a.u.c. 578 (b.c. 145), as
mentioned by Livy (xli. 28).
VI. Pumex, or pumice-stone, is a very light material, calcareous
and full of holes, which is chiefly used for vaulting. The quarries
are on Mount Vesuvius. The vaults of the Colosseum and the
Pantheon are of this light material.
• See Cossi—Trattato delle pietre Pliny calls it Lapis Tusculanus, Nat.
antiche, p. 70. Hist., lib. xxxvi. c. 18.
k This name is applied also to flint.