170 THE STONES OF VENICE CONSTRUCTION

The four-pieced, which is the two-pieced with added joints, rarely occurs, and need not detain us.

§ 14. It will be remembered that in first working out the principle of the arch, we composed the arch of three pieces.¹ Three is the smallest number which can exhibit the real principle of arch masonry, and it may be considered as representative of all arches built on that principle; the one and two pieced arches being microscopic Mont-Cenisian, mere caves in blocks of stone, or gaps between two rocks leaning together.

But the three-pieced arch is properly representative of all; and the larger and more complicated constructions are merely produced by keeping the central piece for what is called a keystone, and putting additional joints at the sides. Now so long as an arch is pure circular or pointed, it does not matter how many joints or voussoirs you have, nor where the joints are; nay, you may joint your keystone itself, and make it two-pieced. But if the arch be of any bizarre form, especially ogee, the joints must be in particular places, and the masonry simple, or it will not be thoroughly good and secure; and the fine schools of the ogee arch have only arisen in countries where it was the custom to build arches of few pieces.

§ 15. The typical pure pointed arch of Venice is a fivepieced arch, with its stones in three orders of magnitude, the longest being the lowest, as at b₂, Plate 3. If the arch be very large, a fourth order of magnitude is added, as at a₂. The portals of the palaces of Venice have one or other of these masonries, almost without exception. Now, as one piece is added to make a larger door, one piece is taken away to make a smaller one, or a window, and the masonry type of the Venetian Gothic window is consequently three pieced, c₂.

§ 16. The reader knows already where a cusp is useful.² It is wanted, he will remember, to give weight to those side

¹ [Above, ch. x. §§ 2, 3, p. 155.]

² [Above, § 7 of this chapter.]

[Version 0.04: March 2008]