Vaulting of Semicircular Transepts
The vaulting of the transept naturally differs from that in the nave when the former is given a semicircular termination. In Romanesque transepts of this type, the vaults are in the form either of simple half domes, or of tunnel vaults ending in such domes, according as the transept arms are lengthened or left merely in the form of apses. Many churches of both these types, but usually of small size, are to be found in southern France,[293] while others appear in Italy and still others in the north of Europe,[294] where such a church as that of Rolduc (Belgium) was considered by its builders as built in a Lombard manner, “scemate longo-bardico,”[295] indicating that the semicircular transept was thought, at least, to be of Lombard origin. The most highly developed transepts of this tunnel-vaulted, half-domed type are probably those in the church of Saint Mary of the Capitol at Cologne, where a groin-vaulted ambulatory is found around each transept apse. Somewhat similar in plan are the transepts of Tournai cathedral in Belgium (between cir. 1110-1170) [(Fig. 53)], except that here the surrounding aisle is very narrow, and, more important still, the half dome is replaced by a clumsy chevet vault with very heavy ribs, their haunches raised to support a series of ramping and contracting tunnel vaults. This construction is very similar to the framework of such a dome as that of the Baptistery at Florence. Nor is it without advantages, since it greatly reduces the vault thrusts and therefore renders unnecessary the use of flying-buttresses,[296] and at the same time permits the windows to rise above the level of its impost. The next semicircular transept of importance is that of Noyon cathedral
Fig. 53.—Tournai, Cathedral.
(cir. 1140),[297] where there is a developed chevet of what will later be called the buttressing ribbed type.[298] More developed still is the south transept of Soissons cathedral (1176-1207), which possesses an ambulatory in two stories with three bays of trapezoidal four-part ribbed vaults corresponding to each principal vaulting bay. The transept proper is covered by a rectangular vault[299] and a broken-ribbed chevet with very broad window cells. Other examples of semicircular transepts could be cited, both of the Romanesque and Gothic periods,[300] but either they do not present any vaulting forms not already discussed or they will be described in connection with the apse proper. That the plan had a long lease of life, if not a very extensive usage, is shown by the fact that it appears in such seventeenth century churches as that of the Lycée Corneille at Rouen (beg. cir. 1614),[301] and is found in numerous Renaissance churches in which the vaulting returns to the earlier tunnel and half-dome forms.[302]