_Chapels._--From the end of the tenth century, according to M. de Caumont, we shall sometimes find aisles running entirely round the choir or sanctuary and communicating with it by an arcade. Even at this early period there must have been chapels in such aisles. In the twelfth century the disposition to elongate the choirs of important churches became general, and brought with it certain modifications of the plan. The Church of Vignori, which dates from the tenth century, has an apse divided into three chapels, recalling in its arrangement that of the Holy Sepulchre at Jerusalem. The Church of St. Servan, built in the eleventh century, has five chapels round the choir, and the Auvergnat churches--Notre Dame du Port at Clermont, and St. Paul at Issoire among others,--which date from the beginning of the twelfth century, also show in this respect some interesting peculiarities. The importance given to the apse by these rings of chapels can scarcely be too much insisted on. On plan these apsidal chapels are, for the most part, round-ended. They are pierced with one or more round-headed windows, and have segmental vaults. On the outside they are often ornamented by mouldings, modillions, and even by variations in the colour of their stones. Chapels between the buttresses of the nave are rare in several aisled churches of the Romanesque period, but in many such buildings they were added at a later time. The great revolution which took place in the art of building towards the end of the twelfth century had, for one of its results, the multiplication of chapels in the numerous great churches dating from that epoch. The principle of that revolution being to replace the inert masses which had previously resisted the various thrusts by comparatively slender points of support upon which those thrusts could be collected, stability being secured by a scientific calculation of forces, it led, as a natural consequence, to a considerable augmentation of disposable surfaces in the interior. These surfaces, mere curtains between the points of support, were ornamented with vast networks of stone, embracing panels of painted glass, on which the principal events of the Old and New Testaments, and the scenes so vividly outlined in the traditions of the time, were traced with admirable art. Room was found for chapels of considerable size, not only in the walls, or rather between the piers of the apse, but also in those of the side aisles, the bounding walls of which were carried out to the external faces of the buttresses receiving the thrust of the main vault, which buttresses now formed the lateral walls of a continuous line of chapels.