9. Main story, Casa Cavalli.
20. Younger Foscari.
21. Ducal Palace, traceried windows.
22. Porta della Carta.
23. Casa d'Oro.
24. Casa d'Oro, upper story.
25. Casa Facanon.
26. Casa Cavalli, near Post-Office.

It will be seen at a glance that, except in the very early fillet
traceries of the Frari and St. John and Paul, Venetian work consists of
roll traceries of one general pattern. It will be seen also, that 10 and
11 from the Frari, furnish the first examples of the form afterwards
completely developed in 17, the tracery bar of the Ducal Palace; but
that this bar differs from them in greater strength and squareness, and
in adding a recess between its smaller roll and the cusp. Observe, that
this is done for strength chiefly; as, in the contemporary tracery (21)
of the upper windows, no such additional thickness is used.

Figure 17 is slightly inaccurate. The little curved recesses behind the
smaller roll are not equal on each side; that next the cusp is smallest,
being about 5/8 of an inch, while that next the cavetto is about 7/8; to
such an extent of subtlety did the old builders carry their love of
change.

The return of the cavetto in 21, 23, and 26, is comparatively rare, and
is generally a sign of later date.

[Illustration: Fig. II.]

[Illustration: Fig. III.]

The reader must observe that the great sturdiness of the form of the
bars, 5, 9, 17, 24, 25, is a consequence of the peculiar office of
Venetian traceries in supporting the mass of the building above, already
noticed in Vol. II.; and indeed the forms of the Venetian Gothic are,
in many other ways, influenced by the difficulty of obtaining stability
on sandy foundations. One thing is especially noticeable in all their
arrangements of traceries; namely, the endeavor to obtain equal and
horizontal pressure along the whole breadth of the building, not the
divided and local pressures of Northern Gothic. This object is
considerably aided by the structure of the balconies, which are of great
service in knitting the shafts together, forming complete tie-beams of
marble, as well as a kind of rivets, at their bases. For instance, at
_b_, Fig. II., is represented the masonry of the base of the upper
arcade of the Ducal Palace, showing the root of one of its main shafts,
with the binding balconies. The solid stones which form the foundation
are much broader than the balcony shaft