For nearly a century the architectural history is a blank. Early in the thirteenth century the wooden ceiling of the nave was replaced by the present quadripartite vault. This involved the demolition of the Norman clerestory, except the jambs of its outer arches, which may still be seen, enriched with zigzag. The north chapel of the crypt also was vaulted, and two windows were inserted in the eastern chapel of the crypt. About the middle of the century were built the north doorways of the cloister, and the vaulted passage in its north-east corner; also part of the west front of the nave was reconstructed. A little later was built, now moved to the north transept, the reliquary (or perhaps it is a gateway), one of the most lovely designs of the thirteenth century, worthy to be put in comparison with the Beverley staircase and the western porches of Ely and St. Albans. Of the time of Henry III. is the oak effigy of Robert Courthose, Duke of Normandy, eldest son of the Conqueror (_d._ 1135), which lies on a wheeled chest of the fifteenth century, and was formerly placed in the centre of the choir. On the whole, there was not much to show at Gloucester, with the exception of the nave-vault, for the long period 1150 to 1318. But about the latter year the Norman south aisle of the nave had got into a very dangerous condition. The north aisle was safe, its wall being propped up by the cloister roof. But the vault of the south aisle had thrust the wall eleven inches out of the perpendicular. To save the vault, Abbot Thokey built on to the Norman pilasters the present beautiful buttresses. But the new buttresses also swung over four inches, and the Norman vaulting had to be taken out; the aisle received a new vault, and its eastern bays were enriched with ball-flower. The beautiful windows are of late Geometrical character, and are smothered in ball-flower. The profuse employment of ball-flower is quite a characteristic of the fourteenth-century Gothic of the West country; it is equally remarkable in the grand windows of Leominster, and at Ledbury and Hereford. “A horizontal line drawn just below the spring of the arch of each window at Gloucester cuts through thirty-two bands of ball-flower.” There are no less than 1400 ball-flowers in each window. [Illustration: RELIQUARY.]