A more original method of transept vaulting is to be seen in certain churches of the school of Auvergne, among them Notre Dame-du-Port at Clermont-Ferrand (Puy-de-Dôme) (eleventh and twelfth century) (Figs. 49, 50) and Saint Étienne at Nevers (Nièvre) (cir. 1097).[285] Here each arm of the transept is divided into two distinct vaulting bays by a transverse arch continuing the line of the outer wall of the church. All the projecting portion is then covered by a tunnel vault, while that bay which corresponds to a continuation of the side aisles is covered by a half tunnel vault, its axis at right angles to the transept proper and rising from above the crown of the intermediate transverse arch to the springing of the crossing dome (Figs. 49-50). Such a vault has much to commend it, for it is most logical in affording excellent abutment for the dome, and at the same time it receives abutment from the tunnel vault of the outer transept bay. Curiously enough, one church of the school, namely that at Orcival (Puy-de-Dôme) (twelfth century),[286] while following the main lines laid down by the vaults just described, differs from them in having full tunnel vaults instead of half tunnels abutting the dome. This is a less satisfactory form in that these vault have to be excessively high in order to bring their thrusts to the proper level, but they do possess the advantage of providing excellent window space above the transept roofs. [Illustration: FIG. 50.--CLERMONT-FERRAND, NOTRE DAME-DU-PORT.] TRANSEPTS WITH RIBBED VAULTING FIVE-PART RIBBED VAULTS