nts, the lowest consisting of the main
arch and piers, the highest of a window or windows, known as the
clerestory, and the middle, called the triforium, consisting usually of
an arcade, sometimes blind, sometimes pierced, and occasionally even
glazed. This triforium fills up the space between the top of the main
arches and the bottom of the clerestory window which is covered on the
outside by the roof of the aisle. As a distinct division or
architectural feature, the triforium arcade is not a necessary part of
the structure. In smaller churches it seldom exists. But in most
cathedrals, as at York, a passage runs behind it, and is generally lit
by the holes in the arcading. As has been stated, however, the arcading
is often blank, and in such cases there might be nothing but a bare
space of wall in its place, for all the practical purpose it serves.
Since, therefore, its form is not dictated by considerations of utility,
there is far more variety in its treatment than in that of the other two
divisions, the main lines of which are formed by structural necessities;
and yet the success or failure of an interior often depend upon the
arrangement and proportion of the triforium; and the arrangement of the
triforium, its emphasis or subordination, was one of the chief problems
with which the builders of Gothic churches had to deal. Since such a
church is generally divided into three storeys, the main lines of the
interior would naturally be expected to be horizontal, and in many
interiors of the Norman and Early English periods they are so, as, for
instance, in the nave of Wells Cathedral. But the stone vault, which
played so important a part in the development of Gothic style naturally
emphasised, with its ribs converging at regular intervals, the vertical
division into bays as opposed to the horizontal division into storeys.
The supports of the outside wall were gradually concentrated by the use
of pinnacles and flying buttresses placed between the windows; the
windows themselves grew in size with the introduction and development of
tracery and the increasing taste for the decoration of stained glass;
until the final organism of Gothic architecture was attained, and the
typical Gothic Church, from being a building of three storeys, pierced
by windows, became a structure made up of vertical supports, with the
intervening spaces filled with glass. When this phase of development was
reached, the building became as organic in al