e
materials. The first thing, therefore, which the student during his
visit to the city ought to do, is to make himself acquainted with the
different varieties of marble that have been found within the walls or
in the neighbourhood. For this purpose the Museum in the Collegio
della Sapienza or University of Rome will afford invaluable aid. In
this institution, conveniently arranged in glass cases, are no less
than 607 specimens of various marbles and alabasters used by the
ancient Romans in the building or decoration of their houses and
public monuments. The collection was made by the late Signor
Sanginetti, Professor of Mineralogy in the University, and is quite
unique. A great deal of instruction may also be obtained from the
mineralogical study of the thousands of marble columns still standing
in the older churches and palaces of Rome, most of which have been
derived from the ruins of ancient temples and basilicas. Several
excellent books may also be consulted with advantage--especially
Faustino Corsi's Treatise on the Stones of Antiquity, _Trattato delle
Pietre Antiche_, which is the most approved Italian work on the
subject, and from which much of the information contained in the
following pages has been obtained.

No marble quarries exist in the vicinity of Rome. The Sabine Hills are
indeed of limestone formation, and large masses of travertine, a
fresh-water limestone of igneous origin, occur here and there, but no
mineral approaching marble in texture and appearance is found within a
very considerable radius of the city. The nearest source of supply is
at Cesi, near the celebrated "Falls of Terni," about forty-five miles
from Rome, where "Cotanella," the red marble of the Roman States, is
found, of which the great columns supporting the arches of the side
aisles of St. Peter's are formed. The hills and rocks of Rome are all
volcanic, and only the different varieties of eruptive rock were first
employed for building purposes. The oldest monuments of the kingly
period, such as the Cloaca Maxima, the Mamertine Prison, the Walls of
Servius Tullius, and some of the earliest substructures on the
Palatine Hill, were all built of the brown volcanic tufa found on or
near their sites. This is the material of which the famous Tarpeian
Rock and the lower part of most of the Seven Hills is composed. It is
the oldest of the igneous deposits of Rome, and seems to have been
formed by a conglomerate of ashes and fragments of pu