The interior is very magnificent. The columns, arches, and walls generally are of brick, now coloured and whitewashed (but originally intended to be seen, as is evident from parts of the incomplete work where the internal brickwork is still exposed and is executed with the greatest care), the capitals and bases being all of stone. The columns of the nave are bold clusters; they are about sixty feet from centre to centre, rather short in proportion to the height of their capitals, which are carved with stiff foliage. Above these is a large pier running up to carry the groining, and there are pointed arches opening to the aisles of very lofty pitch, but which, owing to their great size, certainly look very attenuated. Two chapels open into each bay of the aisles: these are lighted by the large four-light windows already mentioned, whilst both nave and aisles have no windows except cusped circular ones of no great size, placed as near as possible to the groining, which is very simple throughout the church. There is scarcely a horizontal string-course or a label to be seen, and the mouldings are few and simple; yet, nevertheless, the effect is grand. Such a church may well trouble the mind of the English student who thinks that no building is complete which has not its arcade, its triforium, and its clerestory. One of our puny churches would stand—nave, aisles, chancel, tower, and spire and all—within one of the bays of the nave and aisles here; and there is a grand sense of restraint and simplicity about this work which impresses me more each time I see it. At the same time the interest is of this grand kind—there is a sense of the immense and infinite, but no condescension to the love of detail and delight in dainty variety which undoubtedly strikes us in most good Gothic works, and makes them so enjoyable.
The church which inspired the design of this was, no doubt, the cathedral at Florence. But of the two the design of San Petronio seems to me to be the more beautiful. The addition of chapels beyond the aisles and the traceries in their windows make the design a little less bald and insipid, and also give a somewhat truer impression of the real scale than one has at Florence. But at the best such work does not create enthusiasm. The principal effort of the architect was to build something very big, and he succeeded; unfortunately he so contrived as very nearly to prevent one from quite realizing how vast his work is, and I hardly know a more serious charge that can be made against an architect than this.[68]