the Roman empire, there appeared a fully developed plan for places of
Christian worship. The normal Christian church of the fourth century of
our era was an aisled building with the entrance at one end, and a
semi-circular projection known as the apse at the other. The body of the
building, the nave with its aisles, was used by the congregation, the
quire of singers occupying a space, enclosed within low walls, at the
end nearest the apse. In the apse, raised above the level of the nave,
was the altar, behind which, ranged round the wall, were the seats for
the bishop and assistant clergy. This type of church, of which the
aisled nave and the apse are the essential parts, is known as the
_basilica_. The name, employed to designate a "royal" or magnificent
building, had long been applied to large buildings, whether open to the
sky or roofed, which were used, partly as commercial exchanges, partly
as halls of justice. It is still often said that the Christian basilicas
were merely adaptations of such buildings to sacred purposes. Some of
the features of the Christian plan are akin to those of the secular
basilica. The apse with its semi-circular range of seats and its altar
reproduces the judicial tribune, with its seats for the praetor and his
assistant judges, and its altar on which oaths were taken. The open
galleries, which in some of the earliest Christian basilicas at Rome
form an upper story to the aisles, recall the galleries above the
colonnades which surrounded the central hall of some of the larger
secular basilicas. Again, the _atrium_ or forecourt through which the
Christian basilica was often approached has been supposed to be derived
from the _forum_ in connexion with which the secular basilica was
frequently built.

Sec. 2. However, while the _atrium_ of the Christian basilica is merely an
outer court, the secular basilica, when planned, like the Basilica Ulpia
at Rome, with direct relation to a _forum_, was a principal building in
connexion with the _forum_, but not a building of which the _forum_ was
a mere annexe. Further, when we begin to seek for a complete
identification of the Christian with the secular basilica, we are met by
the obstacle that the secular basilica had no fixed plan. If we try to
trace any principle of development in its plan, we find that this
development is directly inverse to that of the Christian basilica. The
secular basilica, in earlier examples a colonnaded building with its