the
abaci; a feature of peculiar importance in this monument, inasmuch as we
know it to be part of the original construction, by a beautiful little
Gothic wreathed pattern, like one of the hems of garments of Fra
Angelico, running along the iron bar itself. So carefully, and so far,
is the system of decoration carried out in this pure and lovely
monument, my most beloved throughout all the length and breadth of
Italy;--chief, as I think, among all the sepulchral marbles of a land of
mourning.

FOOTNOTES:

[49] At least I cannot find any account of it in Maffei's "Verona,"
nor anywhere else, to be depended upon. It is, I doubt not, a work
of the beginning of the thirteenth century. Vide Appendix 19, "Tombs
at St. Anastasia."

CHAPTER XII.

THE ARCH LOAD.

Sec. I. In the preceding enquiry we have always supposed either that the
load upon the arch was perfectly loose, as of gravel or sand, or that it
was Mont-Cenisian, and formed one mass with the arch voussoirs, of more
or less compactness.

[Illustration: Fig. XXXV.]

In practice, the state is usually something between the two. Over
bridges and tunnels it sometimes approaches to the condition of mere
dust or yielding earth; but in architecture it is mostly firm masonry,
not altogether acting with the voussoirs, yet by no means bearing on
them with perfectly dead weight, but locking itself together above them,
and capable of being thrown into forms which relieve them, in some
degree, from its pressure.

Sec. II. It is evident that if we are to place a continuous roof above the
line of arches, we must fill up the intervals between them on the tops
of the columns. We have at present nothing granted us but the bare
masonry, as here at _a_, Fig. XXXV., and we must fill up the intervals
between the semicircle so as to obtain a level line of support. We may
first do this simply as at _b_, with plain mass of wall; so laying the
roof on the top, which is the method of the pure Byzantine and Italian
Romanesque. But if we find too much stress is thus laid on the arches,
we may introduce small second shafts on the top of the great shaft, _a_,
Fig. XXXVI., which may assist in carrying the roof, conveying great part
of its weight at once to the heads of the main shafts, and relieving
from its pressure the centres of the arches.

[Illustration: Fig. XXXVI.]

Sec. III. The new shaft thus introduced may either remain lifted on the
head of the gre