by a
flat and solid cusp as in 6, or by a pierced cusp as in 4. The effect of
the pierced cusp is seen in the uppermost figure, Plate XVIII. Vol. II.;
and its derivation from the solid cusp will be understood, at once, from
the woodcut Fig. IV., which represents a series of the flanking stones
of any arch of the fifth order, such as _f_ in Plate III. Vol. I.

[Illustration: Fig. V.]

The first on the left shows the condition of cusp in a perfectly simple
and early Gothic arch, 2 and 3 are those of common arches of the fifth
order, 4 is the condition in more studied examples of the Gothic
advanced guard, and 5 connects them all with the system of traceries.
Introducing the common archivolt mouldings on the projecting edge of 2
and 3, we obtain the bold and deep fifth order window, used down to the
close of the fourteenth century or even later, and always grand in its
depth of cusp, and consequently of shadow; but the narrow cusp 4 occurs
also in very early work, and is piquant when set beneath a bold flat
archivolt, as in Fig. V., from the Corte del Forno at Santa Marina. The
pierced cusp gives a peculiar lightness and brilliancy to the window,
but is not so sublime. In the richer buildings the surface of the flat
and solid cusp is decorated with a shallow trefoil (see Plate VIII. Vol.
I.), or, when the cusp is small, with a triangular incision only, as
seen in figs. 7 and 8, Plate XI. The recesses on the sides of the other
cusps indicate their single or double lines of foliation. The cusp of
the Ducal Palace has a fillet only round its edge, and a ball of red
marble on its truncated point, and is perfect in its grand simplicity;
but in general the cusps of Venice are far inferior to those of Verona
and of the other cities of Italy, chiefly because there was always some
confusion in the mind of the designer between true cusps and the mere
bending inwards of the arch of the fourth order. The two series, 4 _a_
to 4 _e_, and 5 _a_ to 5 _e_, in Plate XIV. Vol. II., are arranged so as
to show this connexion, as well as the varieties of curvature in the
trefoiled arches of the fourth and fifth orders, which, though
apparently slight on so small a scale, are of enormous importance in
distant effect; a house in which the joints of the cusps project as much
as in 5 _c_, being quite piquant and grotesque when compared with one in
which the cusps are subdued to the form 5 _b_. 4 _d_ and 4 _e_ are
Veronese forms, wonderfully effect