ITHOUT
THE WALLS, ROME.]

Another description of building is customarily met with in connection
with early Christian churches,--the baptistery. This is commonly a
detached building, and almost always circular or polygonal. In some
instances the baptistery adjoins the atrium or forecourt; but it soon
became customary to erect detached baptisteries of considerable size.
These generally have a high central portion carried by a ring of
columns, and a low aisle running round, the receptacle for water being
in the centre. The origin of these buildings is not so clear as that
of the basilica churches; they bear some resemblance to the Roman
circular temples; but it is more probable that the form was suggested
by buildings similar in general arrangement, and forming part of a
Roman bath. The octagonal building known as the baptistery of
Constantine, and the circular building now used as a church and
dedicated to Santa Costanza in Rome, and the celebrated baptistery of
Ravenna, are early examples of this class of structure. Somewhat more
recent, and very well known, are the great baptisteries of Florence
and Pisa.

A few ancient circular or polygonal churches remain which do not
appear to have been built as baptisteries. One of these is at Rome,
the church of San Stefano Rotondo; but another, more remarkable in
every way, is at Ravenna, the church of San Vitale. This is an
octagonal building, with a large vestibule and a small apsidal choir.
The central portion, carried by eight arches springing from as many
lofty and solid piers, and surmounted by a hemispherical dome, rises
high above the aisle which surrounds it. Much elegance is produced by
the arrangement of smaller columns so as to form a kind of apsidal
recess in each of the interspaces between the eight main piers.

Another feature which has become thoroughly identified with church
architecture is the bell-tower, or campanile. This appendage, there
can be no doubt, originated with the basilicas of Italy. The use of
bells as a call to prayer is said to have been introduced not later,
at any rate, than the sixth century, and to this era is attributed a
circular campanile belonging to Sant' Apollinare in Classe at Ravenna,
a basilica already alluded to. The circular plan was, however,
exceptional; the ancient campaniles remaining in Rome are all square;
they are usually built of brick, many stories in height, and with a
group of arched openings in each story, and