174 THE STONES OF VENICE CONSTRUCTION

may, perhaps, be of some service to us afterwards: here we have nothing more to do with it than to note that, thus built, and properly backed by brickwork, it is just as strong and safe a form as that at n; but that this, as well as every variety of ogee arch, depends entirely for its safety, fitness, and beauty on the masonry which we have just analysed; and that, built on a large scale, and with many voussoirs, all such arches would be unsafe and absured in general architecture. Yet they may be used occasionally for the sake of the exquisite beauty of which their rich and fantastic varieties admit, and sometimes for the sake of another merit, exactly the opposite of the contructional ones we are at present examining, that they seem to stand by enchantment.¹

§ 22. In the above reasonings, the inclination of the joints of the voussoirs to the curves of the arch has not been considered. It is a question of much nicety, and which I have not been able as yet fully to investigate: but the natural idea of the arrangement of these lines (which in round arches are of course perpendicular to the curve) would be that every voussoir should have the lengths of its outer and inner arched surface in the same proportion to each other. Either this actual law, or a close approximation to it, is assuredly enforced in the best Gothic buildings.

§ 23. I may sum up all that it is necessary for the reader to keep in mind of the general laws connected with this subject, by giving him an example of each of the two forms of the perfect Gothic arch, uncusped and cusped, treated with the most simple and magnificent masonry, and partly, in both cases, Mont-Cenisian.

The first, Plate 5, is a window from the Broletto of Como. It shows, in its filling, first, the single-pieced arch, carried on groups of four shafts, and a single slab of marble filling the space above, and pierced with a quatrefoil (Mont-Cenisian, this), while the mouldings above are each constructed with a separate system of voussoirs, all of them shaped, I think, on

¹ [For this effect in Venetian Gothic, see next volume, ch. vii. § 10.]

[Version 0.04: March 2008]