§ XIX. I have said that the two orders, Doric and Corinthian, are the roots of all European architecture. You have, perhaps, heard of five orders; but there are only two real orders, and there never can be any more until doomsday. On one of these orders the ornament is convex: those are Doric, Norman, and what else you recollect of the kind. On the other the ornament is concave: those are Corinthian, Early English, Decorated, and what else you recollect of that kind. The transitional form, in which the ornamental line is straight, is the centre or root of both. All other orders are varieties of those, or phantasms and grotesques altogether indefinite in number and species.[18] § XX. This Greek architecture, then, with its two orders, was clumsily copied and varied by the Romans with no particular result, until they begun to bring the arch into extensive practical service; except only that the Doric capital was spoiled in endeavors to mend it, and the Corinthian much varied and enriched with fanciful, and often very beautiful imagery. And in this state of things came Christianity: seized upon the arch as her own; decorated it, and delighted in it; invented a new Doric capital to replace the spoiled Roman one: and all over the Roman empire set to work, with such materials as were nearest at hand, to express and adorn herself as best she could. This Roman Christian architecture is the exact expression of the Christianity of the time, very fervid and beautiful--but very imperfect; in many respects ignorant, and yet radiant with a strong, childlike light of imagination, which flames up under Constantine, illumines all the shores of the Bosphorus and the Ægean and the Adriatic Sea, and then gradually, as the people give themselves up to idolatry, becomes Corpse-light. The architecture sinks into a settled form--a strange, gilded, and embalmed repose: it, with the religion it expressed; and so would have remained for ever,--so _does_ remain, where its languor has been undisturbed.[19] But rough wakening was ordained for it.