In practice the matter has been, I suppose, regulated almost altogether by convenience, the western doors being single in small churches, while in the larger the entrances become three or five, the central door remaining always principal, in consequence of the fine sense of composition which the mediæval builders never lost. These arrangements have formed the noblest buildings in the world. Yet it is worth observing[55] how perfect in its simplicity the single entrance may become, when it is treated as in the Duomo and St. Zeno of Verona, and other such early Lombard churches, having noble porches, and rich sculptures grouped around the entrance. § VII. However, whether the entrances be single, triple, or manifold, it is a constant law that one shall be principal, and all shall be of size in some degree proportioned to that of the building. And this size is, of course, chiefly to be expressed in width, that being the only useful dimension in a door (except for pageantry, chairing of bishops and waving of banners, and other such vanities, not, I hope, after this century, much to be regarded in the building of Christian temples); but though the width is the only necessary dimension, it is well to increase the height also in some proportion to it, in order that there may be less weight of wall above, resting on the increased span of the arch. This is, however, so much the necessary result of the broad curve of the arch itself, that there is no structural necessity of elevating the jamb; and I believe that beautiful entrances might be made of every span of arch, retaining the jamb at a little more than a man's height, until the sweep of the curves became so vast that the small vertical line became a part of them, and one entered into the temple as under a great rainbow. § VIII. On the other hand, the jamb _may_ be elevated indefinitely, so that the increasing entrance retains _at least_ the proportion of width it had originally; say 4 ft. by 7 ft. 5 in. But a less proportion of width than this has always a meagre, inhospitable, and ungainly look except in military architecture, where the narrowness of the entrance is necessary, and its height adds to its grandeur, as between the entrance towers of our British castles. This law however, observe, applies only to true doors, not to the arches of porches, which may be of any proportion, as of any number, being in fact intercolumniations, not doors; as in the noble example of the west front of Peterborough, which, in spite of the destructive absurdity of its central arch being the narrowest, would still, if the paltry porter's lodge, or gatehouse, or turnpike, or whatever it is, were knocked out of the middle of it, be the noblest west front in England.