Between the roof and the vault there is a curious chamber which reminds one of the crater of a volcano, and the impression is increased by the sponge-like stone, which has some resemblance to tufa. The open arcade under the roof has served to keep the woodwork in remarkably sound condition.
The Undercroft.—Much of the external beauty of the chapter-house, as well as the charm of its staircase, is due to its unusual height above the ground. It rests upon a vaulted chamber or undercroft, which is popularly called the crypt, though that term is not very accurate, as the chamber is not sunk underground, but stands almost on a level with the floor of the church. The innumerable springs in the soil of Wells do not, indeed, admit of a subterranean building. The undercroft was finished before the chapter-house staircase was begun; perhaps its walls were built at the end of Jocelin's episcopate; at any rate it was finished by 1286, and represents the last development of the Early English style. It was used as the treasury, where the vestments, ornaments, registers, and other precious things, both of the bishop and chapter, were kept, and, to increase the security of its massive walls, the sacristan had to sleep within them every night.
It is reached by a dimly-lit, impressive passage, which is entered from the north choir aisle through a doorway with deeply-sunk mouldings and carved capitals. Two heads, slanting inwards in a rather awkward manner, support the curious pediment-shaped canopy over the doorway. At the commencement of this fine passage, just within the doorway, is a small vault supported on extremely odd corbels, as if the mason had taken advantage of the obscurity to wanton with his craft. One is a large head with enormous cheeks, apparently suffering from acute neuralgia; a handkerchief, under which a few comically-stiff curls escape, covers the head and is tied under the chin; another represents two dragons biting each other, with a head upside down beneath them; another, which reminds one of the worst eccentricities of modern crockery, is formed by a hand holding a foliated capital. I suppose that the head with swollen cheeks is really another testimony to St. William Bytton's power over the toothache. The undercroft itself was finished before 1286, perhaps some time before; but the more advanced sculpture of the passage looks as if that part were built in the "toothache" period—that is to say, some ten years or so after Bytton's death in 1274.
Certainly the bosses of the vault in the passage beyond the doorway are of a character that suggests the transition to Decorated which was in progress at this time. They are elaborate, and, with one exception, through-carved. The first from the door represents a head, the next an Agnus Dei, the next two grotesque heads joined together, then apparently the Serpent tempting Eve, then an ox, dragons, two small grinning heads, with animals apparently biting them on one side. The corbels are carved into heads, some crowned, others reversed with the shaft in their mouths. On the right-hand side, as one enters the undercroft, a pretty stone lantern projects from the wall; of the little mullions which form its face, one is set far enough from the wall to admit of the insertion of a lamp.