It is a curious instance of an experiment, the object of which was the getting over those difficulties afterwards removed by the invention of the intersecting vault. In the meantime this Tournus roof offered some advantages well worthy of consideration. The first of these was that the thrust of the vault was wholly longitudinal, so that only the supporting arches of the transverse vaults required to be abutted. These being low and in a well-defined direction were easily provided for. Another advantage was, that it allowed of a large and well-defined clerestory, which, as we have seen, was impossible with the longitudinal vaults. On the other hand it might seem to be a fatal objection that the eye instead of being conducted pleasingly along the vault was continually interrupted by a series of cross barrel vaults; this objection, however, is more theoretical than practical, for, owing to the abundant light which enters through the clerestory windows (not suggested at all in the woodcut), and the fact that from the west end looking down the nave the barrel vaults are scarcely seen, the general effect is most pleasing, and it is singular that so happy a solution of the problem, both artistically and constructively, should not have been followed, or that this should be an unique example. The columns in the apse are carried on a podium 6 ft. high, similar to that found in the Holy Sepulchre, which was built by the Crusaders, and constitute a pleasing variety to the ordinary apsidal termination. A crypt of much earlier date exists under the whole choir, and is specially interesting as showing in its vault the rough centering on which it was apparently built. [Illustration: 601. Plan of Abbey Church at Cluny. (From Lorain’s ‘Histoire de l’Abbaye.’) Scale 100 ft. to 1 in.] In the nave of this church all the arches are circular; in the choir, which dates early in the 11th century, if not before, and which is perhaps older than the nave, the great transverse arches are slightly pointed, and support at the intersection a dome (the pendentives of which are formed of squinches carried on wall-shafts), which forms the most beautiful feature in the church. Similar features are found in the churches of le Puy-en-Vélay, St. Martin d’Ainay at Lyons and elsewhere. The pride of Burgundy was the great abbey church of Cluny, which, with its narthex or ante-church, measured 580 ft. in length, or considerably more than any other church erected in France in any age. Its nave was throughout 37 ft. 6 in. in width, and it had double side-aisles, making the total internal width 120 ft., while the whole area covered by it was upwards of 70,000 sq. ft. But colossal as these dimensions are, they convey no adequate idea of its magnificence. The style throughout was solid and grand, and it must have possessed a degree of massive magnificence which we so frequently miss among the more elegant beauties of subsequent erections.