Such is the purpose of the upper story. An ingenious critic who did not seem to know this vindicates it on the plea that "uninterrupted altitude of the bulk in the same plane, is absolutely necessary to the substructure of the mighty dome."[80] No doubt the size of the dome requires a proportionate rise in the lower elevations; but the fact remains that the exterior and interior do not correspond. A greater authority than this critic has thus defined good architecture: "The essence of good architecture of any kind is that its constructive system should be put boldly forward, that its decorative system should be such as in no way conceals or masks the construction, but makes the constructive features themselves ornamental."[81] And at his uncle's cathedral of Ely, Wren might have borrowed and worked out an idea which would have silenced all accusation of fraud and deceit. There, in the central part of the choir on the south side, the roof was removed and placed lower down centuries ago, the better to light up certain shrines below. This roof was never restored to its original position; and the upper stage of the wall is pierced with empty windows through which flying-buttresses can now be seen. The effect, though altogether unusual, is far from displeasing; and the spectator who remembers that Wren was perfectly familiar with this building, is led to wonder why he did not by piercing the niches, imitate Ely at St. Paul's.
The Windows, round-headed and without tracery, contrast unfavourably with the Lancet and Decorated. Wren recognised the value of tracery, as is evident from his remarks on Salisbury Cathedral, although he objected to the Perpendicular mullions and transoms.[82] Yet it is difficult to see how he could have devised anything more elaborate or graceful to harmonise. The carving above and below, in the conventional festoons of the day, is almost universally voted as respectable and nothing more. Mr. Ruskin is very severe on these festoons, on the ground that they are tied heavily into a long bunch thickest in the middle, and pinned up by both ends against a dead wall, and contends that the architecture has no business with rich ornament in any place. Yet he admits that the sculpture is as careful and rich as may be; and let any one study, for instance, the window immediately east of the south portico, and particularly below, where the details can be better observed. In spite of a heavy top-coat of smoke, the combination of cherubs, birds, grapes, and foliage is as graceful and artistic as possible; and the work beneath the east end and north transept windows will also well repay careful study. These details are apt to be neglected, possibly because they seem dwarfed by the immense proportions of the building.[83]