rted as a
line of separation between the nave arcade and the triforium, and also
between the triforium and clerestory. The triforium itself remained as
it had been before 1186; but the clerestory was dressed again, so that
it obtained quite a new character. It was re-faced with the
fine-grained stone, and the slight shafts which supported the
clerestory arcades were provided with Purbeck capitals and bases. This
arcading itself was also changed from its earlier type. The central
arch was still made round in form, but those on either side of it were
each pointed, and all were more finely moulded than before. Above this
point rises the new stone vault, which is carried upon a framework of
strong transverse and diagonal ribs. Between these the shell, or
filling, which formed the surface of the vault, is of chalk, roughly
cut and irregularly laid; above this was placed a thick coat of
concrete.

Some flying-buttresses were built now in order to meet the thrust
exerted by the new arched vault of the nave. These were constructed in
two series, one being concealed under the sloping roof over the
triforium and acting in place of the earlier round-arched abutment.
Its supports were provided at the points where the transverse and
diagonal arches of the nave vault began to spring away from the
vertical plane of the walls. The other series was the immediate
counter-poise to any direct thrust exerted by the arching of the vault
against the upper section of the same walls. There was, in fact, a
large buttress added to support these nave walls at that point from
which each set of vault-carrying ribs began to rise. This buttress,
though apparently sub-divided, was one thing, but of composite
structure. It was pierced first by the aisle, next by the triforium,
and then again above the roof of the triforium. It will be seen that
most of these alterations were the direct result of the introduction
of a stone vault. But the almost entire renewal of the eastern part
of the cathedral was made possible by the destruction and total
removal of the apsidal terminations of the earlier work. It has been
suggested that the fire may have so badly damaged this portion as to
allow no alternative but rebuilding. What may have been the actual
cause of its removal it is impossible for us now to know; but the
substitute is quite a perfect piece of work of its kind. This
ambulatory, or presbytery, as it is commonly misnamed, was nearly all
newly built fr