Alan of Walsingham conceived the idea of obtaining a much larger area in the centre of the cathedral, and instead of rebuilding the piers of the tower he took as the base of his design a central octagonal space, the width of which was equal to that of nave and aisles, with wide arches to nave, transepts and choir, and smaller arches across the octagonal sides; from shafts in the eight pier angles, ribs in wood project forward and carry a smaller octagon on which the lantern rests. Internally the effect of this central octagon is of great beauty and originality, and it is the only instance of such a feature in English Gothic architecture. (See Architecture, Plate VIII., fig. 82.)
The earliest example of the chevet is probably to be found in the church of St Martin at Tours; this was followed by others at Tournus, Clermont-Ferrand, Auxerre, Chartres, Le Mans and other churches built during the great church-building period of the 11th century. In the still greater movement in the 12th century, when the episcopacy, supported by the emancipated communes, undertook the erection of cathedrals of greater dimensions and the reconstruction of others, in some cases they utilized the old foundations, as in Chartres (fig. 5), Coutances and Auxerre cathedrals, while in others (as at Le Mans) they extended the eastern termination, much in the same way as in many of the early examples in England, with this important difference, that when the apsidal east end was given up (about the middle of the 12th century) in favour of the square east end in England, the French, on the other hand, developed it by doubling the choir aisles and adding to the number of extra chapels; thus in Canterbury, Norwich and Gloucester, there were only three apsidal chapels in the chevet, whereas in Noyon (1150), Soissons (1190), Reims (1212), Tours, Seez, Bayeux (1230), Clermont (1275), Senlis, Limoges, Albi and Narbonne cathedrals there were five; in Amiens, Le Mans and Beauvais, there were seven apsidal chapels, and in Chartres cathedral nine. Double aisles round the choir, of which there are no examples in England, are found in the cathedrals of Paris, Bourges and Le Mans; the cathedral of Sens (fig. 6) (1144–1168) possesses one feature which is almost unique, viz. the coupled columns of the alternate bays of nave and choir and of the apse; and these were introduced into the chapel of the Trinity in Canterbury cathedral, probably from the designs of William of Sens, by his successor William the Englishman. The square east end found no favour in France—Laon, Poiters and Dol being the only cathedral examples; and of the triapsal arrangement, viz. with apses in the axes of the choir aisle and a central apse, the only example is that of the cathedral of Autun. The immense development given to the eastern limb of the French cathedrals was sometimes obtained at the expense of the nave, so that, notwithstanding the much greater dimensions compared with English examples, in the latter the naves are much longer and consist of more bays than those in France.
In one of the French cathedrals, Bourges, there is no transept; on the other hand there are many examples in which this part of the church is emphasized by having aisles on each side, as at Laon, Soissons, Chartres, Reims, Amiens, Rouen and Clermont cathedrals. Transept aisles in England are found in Ely, York, Wells and Winchester cathedrals, in the last being carried round the south and north ends of the transept; aisles on the east side of the transept only, in some cases probably for