umbent mass to consider.

Wren's path, then, was beset with difficulties, and he must have
turned to his uncle's cathedral at Ely for enlightenment. In the
earlier years of the fourteenth century the central tower at Ely
collapsed: and the Sacrist, Alan de Walsingham, who acted as
architect, seeing that the breadth of his nave, choir, and transepts
happened to agree, took for his base this common breadth, and cutting
off the angles, obtained a spacious octagon. The four sides
terminating the main aisles are longer than the four alternate sides
at the angles of the side aisles; but at Ely this presents no
difficulty, owing to the use of the pointed arch. As you stand in the
centre of the octagon under the lantern you see eight spacious arches
of two different widths, all springing from the same level and rising
to the same height of eighty-five feet, the terminal arch of the
Norman nave pointed like its opposite neighbour of the choir. Amongst
Gothic churches the interior of Ely reigns unique and supreme,
certainly in England, if not in Europe.[98] Wren was familiar with
this cathedral, and even designed some restorations for it; and he
adopted the eight arches in preference to any possible scheme of four
great arches of sixty feet: but the use of the round arch, as distinct
from the pointed, deprived him of Sacrist Alan's liberty, who without
incongruity made his intermediate arches of the shorter sides,
springing from the same level, rise to the same height as the others.
Wren was compelled to make use of some expedient to reconcile his two
different spaces between piers of forty feet and twenty-six feet, and
accordingly arched these four smaller intermediate spaces as follows.
A smaller arch, rising from the architrave of the great pier, spans
each shorter side of the octagon, and has a ceiling or quarter dome in
the background, coming down to the terminal arches of the side aisles.
A blank wall space above is relieved by a section of an ornamental
arch of larger span, resting on the centre of the cornice; and above
this a third arch, rising from the level of the triforium cornice,
rests more upon the _outer_ side of the great supporting pier, and
thereby obtains the required equal span of forty feet, and equal
height of eighty-nine feet from the ground. This also has a quarter
dome; and the platform beneath on a level with the clerestory is
railed.

The reduction of the octagon to the circle is facilitated by givin