TRANSEPT, in architecture, a transverse section or portion of a hall or building, of considerable relative size, its main dimension being at right angles to the long dimension of the building or hall proper, thus developing a plan of either cruci form or T shape, especially in ecclesiastical architecture, the arms of the church, at right angles to the nave. Transepts are found in several of the large early Christian basilicas of Rome, taking the shape of a large, unbroken, transverse hall, whose length is equal to the combined width of nave and aisles, and separated from the nave by a great arch known as the triumphal arch.
In the opposite wall an arch of similar size leads into the apse. In later basilicas the transept became reduced in importance and the nave ran through unbroken to the apse.
The typical basilica plan, however, has no transept at all, and the transept became a common feature only in Byzantine work from the 8th century, as in S. Mark's at Venice (c. 1063). It is perhaps due to Byzantine influence that the transept came to be universal in the Romanesque work of France and, less com monly, in Italy. In Norman work, both in France and England, transepts were highly developed, frequently designed exactly like the naves, with their own side aisles, triforia and clere storeys, as in Winchester cathedral (1079-93). These Norman transepts are long; in S. Georges at Boscherville (I th century), the north, east and south arms are all equal in length. It was probably the opportunity which the transepts furnished for ad ditional altars or for chapels opening out of their eastern sides, as in many Cistercian abbeys, such as Buildwas abbey (1135), that accounts for the universality of the transept. In French ex
amples, outside of Normandy, the projection is frequently less marked, and the transept without side aisles. This became the rule in French Gothic work, in which the transepts often do not project beyond the outer walls of the church, or project slightly.
In England, however, long transepts remained the rule until the Perpendicular period, the west transepts at Lincoln (c. I200) being 225 ft. long, the transepts of York (1230-60) 220 ft. and those of Lichfield (122o-4o) 145 feet. In the further effort to increase the number of altars, smaller transepts placed east of the main transept had already appeared in the abbey church at Cluny (1089), and became common in the great abbey churches in England, appearing first at Canterbury (c. 117o). Other characteristic examples are the eastern transepts of Lincoln (1192), Rochester (c. 1210). The most beautiful of all are the double transepts of Salisbury (begun 1220). Although the greater number of transepts are square ended, certain occasional examples are apse ended, as in the early basilica at Bethlehem (4th cen tury), S. Maria in Capitol and the Holy Apostles (both 12th century, both in Cologne), and the early French Gothic cathedral at Soissons (1175), and that of Noyon (115o). (T. F. H.)