h altar of St. Paul's is supported by four
splendid columns of Oriental alabaster presented to Gregory XVI. by
Mehemet Ali, the viceroy of Egypt. An interesting collection of
beautiful and valuable varieties of alabasters may be made in
connection with the building operations still carried on in the
unfinished facade of the basilica fronting the Tiber.

The well-known _Verde antico_ is not a marble, but a mixture of the
green precious serpentine of mineralogists and white granular
limestone. It may also be called a breccia, for it is composed of
black fragments, larger or smaller, derived from other rocks, whose
angular shape indicates that they have not travelled far from the
spots where they occur. The ancient Romans called it _Lapis Atracius_,
from Atrax, a town in Thessaly, in the vicinity of which it was found.
It can hardly be distinguished, except by experts, from the modern
green marbles of Vasallo in Sardinia, and Luca in Piedmont. It occurs
somewhat abundantly in Rome, having been a favourite material with
the old Romans for sheathing walls and tables. Magnificent columns of
it were introduced into the temples and triumphal arches. We find
relics of these in the older churches. Four splendid fluted Corinthian
columns of Verde antico, with gilded capitals, support the pediment of
the high altar in Sta. Agnese, in the Piazza Navone, which formerly
belonged to the Arch of Marcus Aurelius in the Corso. A pair of very
fine columns of this precious stone flank each of the niches,
containing statues of the twelve apostles, in the piers which divide
the middle nave from the side ones in the Church of St. John Lateran.
These twenty-four columns are remarkable for the clearness of the
white, green, and black colours that occur in them. They are supposed
to have been taken from the Baths of Diocletian. Two of the splendid
composite columns which support the pediment of the altar in the
Corsini chapel of this church are of this marble, and were also taken
from the Arch of Marcus Aurelius in the Corso. One most magnificent
column of Verde antico has been found, along with seven others of
different marbles, in the wall of the narthex of the subterranean
Church of San Clemente. A small portion of it is polished to show the
beauty of the material, while the rest is dimmed and incrusted with
the grime of age.

Very different from this is the ancient serpentine or ophite of Sparta
called the _Lapis Lacedaemonius_, found in di