28 THE SUSSEX COAST
arches opening into the aisles have more the appearance of being pierced through the walls than of resting on pillars, and the block piers are almost as wide as the openings between them. The aisles were doubtless vaulted, the central roofs had flat wooden ceilings under the tie-beams, and the difficulty of getting tall trees for this purpose probably reduced the width of the building. The blind story, or triforium, has not been altered; it consists of large arches, each enclosing two smaller ones, with a round shaft between and the space above walled with square stones laid diagonally, forming a rude sort of diaper.
Another fire in 1187 consumed nearly the entire city, as Hoveden records, and the cathedral suffered much. The roofs perished, the clearstory walls were seriously weakened, falling debris badly damaged the lower arcades. The rebuilding was begun and carried far by Bishop Seffrid II. (1180-1204), who refaced the lower arches, supplying shafts of Purbeck marble and mouldings of Early English character, built clustered vaulting-shafts up the walls, restored the clearstory with three arches in each bay resting on Purbeck shafts, and provided thick chalk vaulting supported by stone ribs, thus giving to nave and quire the unusual and beautiful character they still possess. To support the vaults very plain and effective flying buttresses without pinnacles were constructed. The west towers had buttresses built against their pilasters and were heightened. The original apse had probably collapsed in the fire (a trace may still be seen just behind the altar-screen on the north) ; in its place the quire was lengthened two bays, the arches round with deep-cut and extremely beautiful mouldings, the pillars almost