ng the Appian and Latin Ways broken pieces of
different kinds may be found in such profusion that such spots look
like the rubbish-heap around a marble quarry. In the vast grounds over
which the imposing ruins of Hadrian's Villa spread, heaps of fragments
of marble flooring or casing may be seen in almost every neglected
corner, from which it is easy to obtain some lovely bit of giallo
antico or pavonazzetto or green porphyry. Beside the ancient quay of
Rome, leading to the ruins of the Emporium or Custom-house--at a spot
called in modern phrase "La Marmorata," because marble vessels still
discharge their cargoes there--immense quantities of marble,
alabaster, and porphyry are piled up, that were unshipped untold ages
ago for Roman use; and a vineyard a short way off, on the slope of
the Aventine, is much frequented by collectors on account of the
richness of its finds.

But it is not as a mere amusement, or as a means of collecting pretty
souvenirs of travel, that such marble-hunting expeditions are to be
recommended. They may have a much higher value. The different kinds of
marble collected are peculiarly interesting owing to their association
with the different epochs of the history of the city and empire; and
as the specimens which the geologist obtains throw light upon the
formation of the rocky strata of the earth, so the small marble
fragments which the student finds in Rome afford a clue to the various
stages of its existence. Indeed, a competent knowledge of the marbles
of Rome is indispensable to a clear understanding of the age of its
ancient monuments. An immense amount of controversy has raged round
some remarkable building or statue, which would have been prevented
had the nature and origin of the marble of which it was composed been
first investigated. The famous statue of the Apollo Belvedere in the
Vatican, for instance, was long regarded as an original production
either of Pheidias himself or of his school. But the discovery that
the marble of which it is wrought is Lunar or Carrara marble--which
was unknown until the time of Julius Caesar, who first introduced it
into Rome--is of itself a proof that it is not a genuine work of Greek
art of the best period, but a monument of the decadence, or a copy of
an original, wrought in imperial times for the adornment of a summer
palace in Italy. In numberless other cases, ancient monuments have
been identified by the mineral character and history of their marbl