The transept. Between the aisles and the apse is sometimes inserted a transverse element, which exists in the great churches of Rome and is called a transept. With respect to the totality of known early Christian buildings, its geographical distribution is very limited, though in the 19th c. it was thought, on the model of Old St. Peter’s, to be an intrinsic element of the Latin Christian basilica. It was much more widespread in the East, esp. in Aegean architecture, than in the West. It is important to distinguish the transept proper from the cruciform plan, which will be examined separately. In its plan, the transept may stop at the lateral fa§ades or, more frequently, go beyond them. It generally ends in a straight wall but, esp. on the Adriatic coasts as at Dodona and Paramizia, we know a number of cases where the arms of the transept end in apses.
Generally we can distinguish three types of plan: 1 the undivided or continuous transept, where the colonnades stop at the height of the transverse aisle and where no architectural division is involved; 2 the compartmental generally tripartite transept, where partitions, organized in various ways resting on massive pillars or on a colonnade of different rhythm from that of the aisles, extend as far as the apse, the division of the quadratum populi into compartments; and 3 the enveloping or cross transept, where the colonnades carry on, enclosing the central space and extending the aisles around the enlarged nave. Then the junction of the roofs poses various problems.
The first type normally involves a double-sloping transverse roof. In the other two there may be a raised central element at the crossing, such as a lantern with trusses or sometimes a cupola see below. The tables of comparative models in A. Orlando’s handbook may be consulted on this point. The raison d’ªtre and function of the transept have aroused endless debate but seem to vary according to cases. At the Vatican and in the great martyria, it may be connected to the need of pilgrims to circulate in order to approach the holy tomb or relics. But it also existed in urban churches. In Greece the arms of the transept seem in some cases to have replaced with suitable alterations the service rooms for the clergy or for the collection of offerings. It is better to conclude with P. Lemerle that the transept corresponds more to an occasional amenity than to an actual necessity, but analysis remains open. III. Liturgical arrangements in the church.