In support of this theory it is possible to point out that if long cross beams were used in building these domes, it would be difficult if not impossible to remove them after the dome was finished. If, however, as at Angoulême, small spaces were left in the masonry it would be possible to tilt a beam bevelled at each end and resting on the ledge of the dome and thus remove it without cutting. Still another argument in favor of this theory is the fact that the open spaces to north and south are above the level of the ledge, which would seem to indicate that they were planned to receive the end of a cross beam at right angles to, and above the one running lengthwise. Of course, when windows took the place of these small recesses the removal of the beam could be made through them. There remain, however, a number of churches in which there are neither windows nor recesses, but in most of these the ledge of the dome is itself wide enough to support a beam which could be removed without striking the vault surface. [Illustration: FIG. 4.--ANGOULÊME, CATHEDRAL.] As for the choirs of the churches of this school, they were occasionally domed as at Saint Front[25] (Fig. 1), but were more often covered by a tunnel vault terminating in the half dome of the apse. The eastern portion of the choir of Saint Front (Fig. 1) and the choir of Angoulême (Fig. 4) illustrate this latter arrangement. NAVES VAULTED WITH DOMES ON SQUINCHES Although very frequently used over the crossing of Romanesque churches, the dome on squinches is seldom found over the bays of the nave. There is in fact no distinct school in which this method is employed and the examples of its use are widely scattered. The principal one is, perhaps, the cathedral of Notre Dame at Le Puy (Haute-Loire), which dates from the eleventh and twelfth centuries. Unlike the domed churches of Perigord it is of basilical plan with side aisles. The nave is in six bays with broad arches opening into the aisles and a triforium arcade above them. Across the nave are transverse arches separating the bays. The four toward the east are semicircular, the remaining two are pointed in elevation. These arches rise from imposts nearly or quite as low as those of the nave arcade, and walls are built upon them to the level of the string-course above the triforium. Six rectangular bays,--or seven including the crossing,--of practically square plan are thus formed and each is covered with a dome. In the western bays,--which are at least a century later than those at the east end and therefore more advanced in structure,--a clerestory wall is erected with a single window in its north and south walls, and openings corresponding to windows from one bay to the next above the transverse arches, to secure a good distribution of light (Fig. 5). Across the upper corners of these four walls and rising from the same level as the window heads, are arches with half domed triangular niches beneath them, converting the square