Thirdly, he rebuilt the central tower on the Norman piers and arches. To lessen the weight as much as possible it was built in two skins, the inner skin consisting of a framework of upright stone girders, as in the towers of Wells and Lincoln. Externally it is smothered in ball-flower. Originally it carried a tall timber spire; the loss of which greatly injures the external elevation of the cathedral. [Illustration: NORTH TRANSEPT AISLE.] Fourthly, he went on with the improvement of the lighting of the cathedral. Beginning probably at the north-east transept, which was rebuilt, together with its eastern aisle, and working along the choir and nave to the west end, and then _vice versa_ on the south side of the cathedral, he took down all but the lower part of the walls of the Norman aisles, rebuilt the upper part higher, and inserted very large windows. This lighted the nave, at any rate, very satisfactorily. The design of these windows is unusual and effective, owing to the largeness of the trefoils employed in the tracery. VIII. CURVILINEAR (1315-1360).—By the time of Swinfield’s death it may be conjectured that the pilgrim-revenue had begun to fall off; for the rebuilding of the south-east transept, together with its eastern aisle, in completion of the reconstructions commenced by Swinfield, was executed in a cheap and inferior way, even the clumsy Transitional plinth being retained for the new central column of the transept. The windows have flowing tracery. To the same period belong the stalls and the beautiful chapter-house, now in ruins. The lead of its roof was cast into bullets in the Civil War; sacrilegious bishops used its stones as a quarry for their palace. There are monuments of Bishop Swinfield (_d._ 1316) and Bishop Charleton (_d._ 1343). It is probable that all this work was done before 1349, when the Black Death made its appearance at Hereford, and again in 1360. IX. PERPENDICULAR (1360-1485).—The lighting improvements were now completed by the insertion of two huge windows in the south transept, the southern of which has recently been filled with magnificent glass by Mr. Kempe. On the north side of the choir Bishop Stanbury (1455-1474) built for himself a pretty little chantry-chapel, like those at Lincoln. It has fan-vaulting. X. TUDOR.—Bishop Audley (1492-1502) built himself a pentagonal chantry-chapel, two stories high, projecting from the south side of the Lady chapel. But, as he was translated to Salisbury, he had the trouble of building another chantry-chapel there. To this period belong the Bishop’s cloister—three-sided, as at Chichester—and probably the Vicars’ cloister, with picturesque timber roof, and a fan-vault over the entrance to the Vicars’ college. Bishop Booth (1516-1535) built the outer north porch—an admirable specimen of late Gothic design.