countries contain a large number of churches of semi-Byzantine, semi-Romanesque character, some of which are as late as the thirteenth century.[30] Most of these are so distinctly Byzantine that they do not properly fall within the province of this book, in spite of their late date; but others, like the cathedral of Molfetta,[31] have a vaulting system quite closely allied to the Romanesque.[32] In this particular cathedral, a nave of three square bays is covered by three domes, one on flattened spherical pendentives, the others on niche-head-squinches. Two of them rise from drums and unlike their Byzantine prototypes, they are all of stone.[33] Moreover, the side aisles are covered with half tunnel vaults on full transverse arches, the crown of the vaults together with the nave walls above them acting as admirable buttresses for the domes. A system not quite so logical exists in the aisles of the church of San Sabino at Canosa (1100), where there are full tunnel vaults which do not serve so adequately as buttresses. PYRAMIDAL VAULTS [Illustration: FIG. 9.--LOCHES, SAINT OURS.] Although not vaulted with domes, the church of Saint Ours at Loches in France (Indre-et-Loire) (Figs. 9 and 10) has a close connection with such churches as those of Perigord and Notre Dame-du-Puy. This collegiate church was probably constructed a little before 1168, and originally consisted of a nave divided into square bays by transverse arches of pointed [Illustration: FIG. 10.--LOCHES, SAINT OURS.] elevation and side aisles which have now disappeared. Each nave bay is converted from a square into an octagon by flat triangular pendentives on very small trumpet arches. But instead of domes, the builders of Saint Ours substituted a hollow octagonal pyramid of stone over each bay. Such a system, while presenting the same aesthetic objection as that of Le Puy, had greater structural advantages. The pyramids could be built entirely without centering, and exerted almost no outward thrust, while the stones of which they were constructed could be faced on the exterior (Fig. 9) as well as the interior, and the steep roof thus formed provided adequate drainage for the rain and snow of the region.[34] TUNNEL VAULTS