Architecture is, however, the central art of the group, which in its highest form combines all the three classes in nearly equal proportions, but not always necessarily so. The Pyramids of Egypt, for instance, though Technically the most wonderful buildings in the world, have very little Æsthetic, and hardly more than one of Phonetic, value. The great temple at Baalbec,—and in fact all the Roman temples, may be classed as containing six parts of Technic value for mechanical excellence of size and construction, four for beauty of form and detail, but certainly not more than two parts for any expression of religion or intellect they may exhibit, making up twenty for the index of their artistic value. Cologne cathedral takes very nearly the same position in the scale, but Rheims, Bourges, and the more perfect Gothic cathedrals may be classed higher, as five Technic, three Æsthetic, and four Phonetic, making twenty-three altogether as their index; and they are only surpassed by such a building as the Parthenon at Athens, which, though not so large and imposing as some others, is, so far as we know, the most perfect building yet erected by man. It owes this perfection mainly to the equal balance of parts. There is nothing so difficult or startling in its construction as there is in most Gothic cathedrals; but what there is is mechanically perfect, both in design and execution. Its form is nearly perfect, combining stability with simplicity and at the same time avoiding monotony or any appearance of greater strength than is absolutely necessary. Its details are all as exquisite in form as the Temple itself, and it was at one time coloured to an extent we can hardly now realise, but which must, when complete, have made it one of the most perfect examples of Æsthetic art. The walls of the cella were almost certainly covered with Phonetic paintings similar to those in the Lesche at Delphi; and the pediment, the metopes, the friezes, were all sculptured to such an extent as to render the Phonetic expression of the building at least equal to either its Technic or its Æsthetic excellence. It is easy to conceive a building, such as a trophy or a mausoleum, in which painting and sculpture shall be relatively more important than they are in this instance, and in which consequently the index may be raised above twenty-four; but if this were so, it ought probably to be classed among works of sculpture or painting rather than as an object of architecture.