V. In the Middle of the Geometrical period, c. 1280, the east end of the Lady chapel was rebuilt, and a window with Geometrical tracery inserted; the tracery is of early character, containing nothing but foliated circles. At the same time it received a simple quadripartite vault; and to resist the thrust of this vault, the northern buttresses were reconstructed and weighted with pinnacles. Of these pinnacles only one, at the north-east corner, remains; the others seem to have been reconstructed at the time when the pinnacles of the choir were built.
CHOIR.
VI. Curvilinear.—But the great building period at Bristol was between 1315 and 1349—that short but brilliant period when English mediæval design was at its best—which culminated in the Octagon and Lady chapel of Ely, the choir-screens of Southwell and Lincoln, and the Percy monument at Beverley. Everything east of the nave was pulled down and rebuilt de novo. And a very remarkable design it is; in fact, quite unique among our cathedrals. All other cathedral authorities had agreed long ago that the cardinal fault in all Romanesque design was its bad system of lighting, but that the remedy was to be found mainly in improving the top-lighting—i.e., in increasing the dimensions of the clerestory. Beverley clerestory had taller windows than Durham; Salisbury clerestory had three windows for every one of Beverley; Exeter spread out its windows in increasing breadth till they touched the buttresses on either side; the clerestories of the choir of Gloucester, now in course of erection, were a vast, lofty, continuous sheet of glass. But there was an alternative system of improving the lighting, which in many large churches, such as Grantham, Ledbury, and Leominster, was the result of fortuitous growth, but which in the choir of the Temple Church, London, and in Patrington Church now in course of erection, was the result of deliberate design. It was to magnify the aisles at the expense of the nave, to lift them up so high that windows of vast height could be placed in their walls, to dispense with a clerestory altogether, and to give to the pier-arcade of the nave the additional height gained by the suppression of the clerestory. It was to substitute side-lighting for top-lighting; to rely exclusively on the flood of light passing from vast, lofty aisle windows into the nave through its elevated arches. Hence the big windows of Bristol choir, each representing a pair of windows; the lower half the usual small window of an aisle, the upper half the larger window stolen from the clerestory.
BERKELEY CHAPEL.
But the new design had another merit, which probably weighed still more with the Bristol builders. The cardinal difficulty of the mediæval builders was how to keep up on the top of lofty clerestory walls a heavy stone vault which was always striving to push them asunder. They succeeded at length in keeping the clerestory walls from being thrust out by propping them up with flying-buttresses, perilously exposed, however, to all the vicissitudes of English weather. But there was another solution of the problem, which had been worked out in the thirteenth century in the Temple Church, and in the twelfth century in many a church in central and southern France, such as the old cathedral of Carcassonne. It was to stop the outward thrusts of the nave vault not by the inert resistance of buttress, pinnacle, and flying-buttress, but by bringing into play opposing thrusts—i.e., the inward thrusts of vaults built over the aisles. But to make these outward and inward thrusts balance and neutralise one another, the aisle vaults must be of pretty much the same height and span as those of the nave. The nave must be lowered or the aisles must be raised, or both. At Bristol the architect has preferred to raise the aisles. Then, the stability of the nave vault being secured, all the builder has to do is to stop the outward thrusts of the vaults of the aisles. This it is easy enough to do by a row of buttresses weighted with pinnacles. So Bristol Cathedral, to eyes accustomed to contemporary cathedrals, presents the strange solecism of having neither clerestory nor flying-buttresses. The whole design may well have been based on that of the English cathedral at Poitiers.
VAULT OF AISLE.