nted arch, which is a contradiction in terms: it
ought to be called a curved gable; but it must keep the name it has got.

Now _a_, _b_, _c_, _d_, Fig. XXX., are the ghosts of the lintel, the
gable, the arch, and the pointed arch. With the poor lintel ghost we
need trouble ourselves no farther; there are no changes in him: but
there is much variety in the other three, and the method of their
variety will be best discerned by studying _b_ and _d_, as subordinate
to and connected with the simple arch at _c_.

Sec. XI. Many architects, especially the worst, have been very curious
in designing out of the way arches,--elliptical arches, and four-centred
arches, so called, and other singularities. The good architects have
generally been content, and we for the present will be so, with God's
arch, the arch of the rainbow and of the apparent heaven, and which the
sun shapes for us as it sets and rises. Let us watch the sun for a
moment as it climbs: when it is a quarter up, it will give us the arch
_a_, Fig. XXXI.; when it is half up, _b_, and when three quarters up,
_c_. There will be an infinite number of arches between these, but we
will take these as sufficient representatives of all. Then _a_ is the
low arch, _b_ the central or pure arch, _c_ the high arch, and the rays
of the sun would have drawn for us their voussoirs.

Sec. XII. We will take these several arches successively, and fixing the
top of each accurately, draw two right lines thence to its base, _d_,
_e_, _f_, Fig. XXXI. Then these lines give us the relative gables of
each of the arches; _d_ is the Italian or southern gable, _e_ the
central gable, _f_ the Gothic gable.

[Illustration: Fig. XXXI.]

Sec. XIII. We will again take the three arches with their gables in
succession, and on each of the sides of the gable, between it and the
arch, we will describe another arch, as at _g_, _h_, _i_. Then the
curves so described give the pointed arches belonging to each of the
round arches; _g_, the flat pointed arch, _h_, the central pointed arch,
and _i_, the lancet pointed arch.

Sec. XIV. If the radius with which these intermediate curves are drawn be
the base of _f_, the last is the equilateral pointed arch, one of great
importance in Gothic work. But between the gable and circle, in all the
three figures, there are an infinite number of pointed arches,
describable with different radii; and the three round arches, be it
remembered, are themselves representative