XXV. The _exterior_ of the great _north transept_ should be especially noticed. The remarkable windows shew to great advantage from the outside, in connection with the massive buttresses, of which those at the angles are turreted, with spiral cappings. The clerestory windows are, as has already (§ XI.) been mentioned, triangular on the exterior, and resemble those in the outer wall of the triforium in the nave of Westminster. The upper window in the north wall opens from the Archive Room, (§ XXIII.) The external sills of all these windows resemble those of the interior, (§ XI.) They were walled up, but have been restored by Mr. Scott from original portions found embedded in the walls, partly in their places, and partly detached. The date of the _central tower_, which rises above this transept, has not been recorded, but it may safely be placed between 1300 and 1310. It was probably undertaken immediately after the completion of the north transept, and the cost of its erection, like that of the transept, was no doubt defrayed from the sums which continued to be offered at the shrine of St. Thomas Cantilupe[42]. The tower (161 ft. high to the top of the pinnacles) is of two stages above the roofs, with buttresses at the angles. (The pinnacles which cap these buttresses are modern, and date from 1830.) The arcades and window-openings, as well as the buttresses, are covered with the ball-flower ornament, which is scarcely anywhere found in such profusion as here, and in the south aisle of the nave of Gloucester; (see that Cathedral). The _Stanbery Chapel_ (§ XIV.) projects between the great and the eastern transept. The graceful Decorated window of the choir aisle, which rises above it, and the Early English arcades which cover the wall of the choir between the clerestory windows, as well as the windows themselves, (see § IX.,) should here be noticed.