The details of the north wall of the presbytery are similar to those described on the south. But there are no sub-arches to any of the flying buttresses, and the slopes of each are protected by lead coverings. And in the exterior of the north aisle the same elements of structure and design may be discovered, even to the presence of twelfth-century remains, the curve of the old encircling apse, and the position of the first sills, abaci, and string-courses. But it should be noticed that in the eastern bay of this aisle externally, where on the south there is a fifteenth-century solid square panel, on the north there is a small round-headed window. But this little window is of no earlier date than the walls in which it is set. The second and third windows from the east buttress of the presbytery aisle are insertions of fifteenth-century type; but they have been so much renewed and restored that only in the third one does there appear to be any portion of the original tracery remaining. On the north side of the choir and presbytery are four very fine old lead rain-water heads and square lead pipes. The east end of the present #Library# has in it five windows. Two of the upper ones are built up, the central and higher one only being glazed. In detail they are all of the same date as the walls they are in. None has any tracery, and by this they show that this piece of work was done at the same time as the chapel--now a vestry--on the east side of the south end of the transept. The gable is a low slope like the present roof, but the slope of the old gable and roof may be seen upon the east wall of the transept. There is one buttress only on the east side of the library. The north side is divided into two parts in its length by a buttress. The parapet has a corbel course similar to that on the two eastern bays of the presbytery aisle. The two small pointed windows below it are built up, as now the apartment they once lighted is a lumber-room, where the remnants of the old reredos are stored. The larger windows below are of the same date, nearly, as those two fifteenth-century ones in the north wall of the presbytery aisle. The east one has three and the west four lights, with cusped tracery in the heads.