be found used in many existing monuments of ancient Rome, such
as the drains of the middle and southern basin of the left bank, the
channels and arches of the Marcia and Anio Vetus, the Servian walls, the
temples of Fortuna Virilis, of Hercules Magnus Custos, the Rostra, the
embankment of the Tiber, etc. The largest and most magnificent quarries
in the suburban district are the so-called Grotte della Cervara. No
words can convey an idea of their size and of the regularity of their
plan. They seem to be the work of a fanciful architect who has hewn out
of the rock halls and galleries, courts and vestibules, and imitated the
forms of an Assyrian palace.

For the study of the peperino mines, which contain a stone special to
the Alban district, formed by the action of hot water on gray volcanic
cinders, the reader should follow on foot the line of the new Albano
railway, from the place called Il Sassone to the town of Marino. Many of
the valleys in this district, now made beautiful by vineyards and
oliveyards, owe their existence to the pickax of the Roman stonecutter,
like the valley of Pozzo Pantaleo. The most curious sight is a dolmen or
isolated rock 10 meters high, left in the center of one of the quarries
to certify the thickness of the bed of rock excavated. In fact, the
whole district is very interesting both to the archeologist and to the
paysagiste. The mines of Marino, still worked in the neighborhood of the
railway station, would count, like the Grotte della Cervara, among the
wonders of the Campagna, were they known to the student as they deserve
to be.

The principal Roman buildings in which the lapis Albanus has been used
are: the Claudian aqueduct, the Cloaca Maxima, the temples of Antonius
and Faustina, of Cybele, of the Eventus Bonus, of Neptune, the inclosure
wall of the Forum Augustum, Forum Transitorium, and Forum Pacis, the
Porticus Argonautarum, Porticus Pompeii, the Ustrinum of the Appian Way,
etc. The sarcophagus of Cornelius Scipio Barbatus in the Vatican
museum, and the tomb of the Tibicines in the Museo Municipale al Celio
are also of this stone.

Travertine stone was quarried in the plains of Tivoli at places now
called Le Caprine, Casal Bernini, and Il Barco. This last was reopened
after an interval of many centuries by Count G. Brazza, brother of the
African explorer. Lost in the wilderness and overgrown with shrubs, it
had not been examined, I believe, since the visit of Brocchi. It can be