There is a massive octagonal pier in the centre, and eight other round piers, which support the vaulting. A piscina in the doorway has a curious sculptured dog gnawing a bone. Here are preserved a cope chest, some stone coffins, and other treasures. Retracing our steps to the aisle, we enter the noble _Staircase_ leading to the chapter-house. It is Early Decorated, the door at the upper end being added in the Perpendicular period, when the Chain Gate was erected. Two Decorated windows light the staircase. The _Chapter-House_, octagonal in plan, is entered by a fine doorway composed of double arches. There is a curious boss here, composed of four bearded heads. There is a central pillar, with clustered shafts of Purbeck marble, from which the beautiful ribs of the vaulted roof spring. There are eight windows, the mouldings of the arches being ornamented with ball-flower, and retaining some old glass. An arcade runs round the wall under the windows, with ornamented canopies, and beneath this are the stone benches. Sculptured heads and grotesques appear in the ornamentation of the arches. This chapter-house is later than the staircase, and was probably built by Bishop William de la Marchia (1293-1302), the vault being added after his time, and finished in 1319. DIMENSIONS Total length 383 ft. Length of nave 161 ft. Breadth of nave 82 ft. Height of nave 67 ft. Length of choir 103 ft. Length of transepts 135 ft. Height of towers 160 ft. Area 29,070 sq. ft. PRINCIPAL BUILDING DATES Early Norman--Font. Transition (1174-1191)--Eastern bays of nave, transepts, north porch, and west bays of choir. Early English (1218-1286)--West front, western part of nave, undercroft of chapter-house, palace. Early Decorated--Staircase to chapter-house. Decorated (1293-1363)--Chapter-house, Lady Chapel, central tower, inverted arches, east part of choir. Perpendicular (1386-1400)--Western towers, gateways, Chain Gate, Deanery. BATH ABBEY