In the south aisle, over the entrance to the sacristy, there is a very charmingly-proportioned gallery which is known as the "minstrel gallery." A gallery of this kind, though not unique, is very rare, but Exeter Cathedral has two--one in the north transept and another in the nave. In this case the arcading has been altered to accommodate this obviously later addition, made probably in the early part of the fifteenth century. Three shafts from the arcade have been left, which support a fan-shaped vaulting, upon which the gallery rests. There is little doubt as to the object of the gallery, though various theories have been advanced. By some it is supposed that it was used by the priest whose duty it was to watch the lights burning on the various altars; others suggest that it was indeed used by the instrumentalists to keep time during the procession, etc.; but, as it is immediately in front of the chapel of the Head of St. Chad, it was no doubt intended for the exhibition of the head to those below in the aisle. However, it may be said that the raised galleries in mediæval halls were always called by the name of "minstrel gallery," and so the name came to be used of galleries generally. This gallery is reached by the staircase in the wall which leads to the upper floor of the sacristy. Just against the entrance to this staircase, in the wall of the aisle, is an ancient piscina. Its presence here is unexplained, as there is no record of a chapel at this spot; though it has been suggested that the altar dedicated to St. Blaise occupied a position in this aisle. It is perhaps worth noticing that in the old days the two bays of the cathedral between the high altar and the Lady Chapel, together with their portions of the aisles, were generally spoken of as the Lady Choir, and are marked as such in old plans; other writers again speak of this part of the building as "the cross aisle." There were gates across the choir aisles in a line with the reredos, and these are marked in the plan of the cathedral published somewhere about 1720. No doubt the eastern ends of the choir aisles in still earlier days were spoken of as St. Andrew's Chapel or St. Nicholas' Chapel; but, though it is almost certain that the east end of the north choir aisle was dedicated to St. Andrew, there is no certain information as to the dedication of the corresponding chapel in the south aisle, but it is generally believed to have contained an altar to St. Nicholas.