nest in Rome, in the nave of Sta. Agnese; the pair of half columns
which support the pediment of the altar in the Capella della
Presentazione in St. Peter's; and the basin of the handsome fountain
in front of the Pillar of Marcus Aurelius in the Piazza Colonna,
constructed by the architect Giacoma della Porta out of an enormous
mass of Porta Santa found lying on the ancient wharf.

Frequent specimens of a beautiful marble known as _Fior di Persico_,
from the resemblance of the colour of its bright purple veins on a
white ground to that of the blossom of the peach, may be found in the
Roman churches. It was much used for mouldings, sheathings, and
pedestals, and also for floors. In the Villa of Hadrian large
fragments of slabs of this marble may be found, which lined the walls
and floors of what are called the Greek and Latin Libraries. The
Portuguese Church in Rome has several columns of Fior di Persico
supporting the pediments of altars in the different chapels;
especially four pairs of fluted ones which adorn the two altars at the
extremity of the nave, which are among the largest and finest in Rome.
But the most splendid specimens of all are a pair of columns in the
Palazzo Rospigliosi. The dado, eight feet in height, in the gorgeous
Corsini chapel in the Church of St. John Lateran, is formed of large
tablets of highly-polished Fior di Persico, and the frieze that
surrounds the whole chapel is composed of the same beautiful material,
whose predominance over every other marble is the peculiarity of this
sanctuary. The ancient name of this marble was _Marmor Molossium_,
from a region in Epirus--now Albania--which was a Roman province in
the time of Pompey. It is associated with the celebrated campaigns in
Italy of Pyrrhus, king of Epirus, in which Greece was for the first
time brought into contact with Rome. The region in which the quarries
existed was the most ancient seat of Pelasgic religion.

The infinite hues and markings of the coloured marbles have all been
painted by Nature with one material only, variously proportioned and
applied--the oxide of iron. The varieties of marble are mainly caused
by the different degrees in which this substance has pervaded them.
They are variable mixtures of the metamorphous carbonates of protoxide
of iron and lime. And it is an interesting fact that there is a
distinct relation between deposits of magnetic iron ore and the
metamorphoses of limestones into marbles; so that this s