During Mr. Billing's restoration in 1856 a remarkable crypt was opened three feet beneath the paving of the choir between the north and south piers of the tower. This crypt, which was covered up again after investigation, was 7 feet long by 5 feet 6 inches, and just high enough for a man to stand upright; its walls were of stone, and contained aumbries or lockers at each end. There were also slight remains of indented crosses on the western side, and at the east enough was missing to suggest a doorway. The entrance to this chamber may have been through a trap-door, or by a passage leading into the east side. It was clearly not intended for sepulture, as its length was from north to south; and the absence of passages giving convenient access on each side seems to prove that it was not intended for the exhibition of relics. The most likely theory is that it was used as a secret chamber to contain the University chest, which was called the Frideswide chest, because it was kept in a secure place in this church, its keys being in the hands of certain canons by appointment of the chancellor. If this seems a very public place for a secret chamber, it must be remembered that originally it was immediately under the rood-loft, and therefore admitted of a trap-door being concealed; though the resting-place of the chest may not have been kept very secret for all we know. This crypt was probably made in Norman times, and is unique of its kind. =The Aisles of the Nave and Transepts= show the progress which was made at the end of the twelfth century in vaulting: Mr. Ruskin says of the work here that it is "bad and rude enough, but the best we could do with our own wits, and no French help." Vaulting originally began with square ribs, after wards the ribs became plain half-rounds, and later were moulded Here we find good specimens of the development of all three stages. In the choir aisles the vaulting arches are partly square and the ribs on the groins half-round, of a heavy character. These ribs were inserted at a later period, as is sufficiently clear from the awkward way they are fitted to corbels at the side of the capitals which carry the vault. In the west aisle of the north transept the vaulting is the same, but lighter in character; and there are no corbels, though the fitting is still awkward. In the north aisle of the nave the vaulting is pointed but still with plain half-round ribs, a little lighter than in the transept-aisles. But in the south aisle of the nave, as the builders got on with their work to the westward, their style underwent a further development, and a pear-shaped moulding with a fillet along the edge proclaims that the Early English period had begun. With the completion of this aisle they seemed to have become bolder; for the vaulting shafts in the transepts with their unmistakable Norman capitals, and the solitary ribbed stones resting on those of the south transept, prove that they