ts point cut off); _f_ part of a
four-sided pyramid. Then, assuming the abacus to be square, _d_ will
already fit the shaft, but has to be chiselled to fit the abacus; _f_
will already fit the abacus, but has to be chiselled to fit the shaft.

From the broad end of _d_ chop or chisel off, in four vertical planes,
as much as will leave its head an exact square. The vertical cuttings
will form curves on the sides of the cone (curves of a curious kind,
which the reader need not be troubled to examine), and we shall have the
form at _e_, which is the root of the greater number of Norman capitals.

From _f_ cut off the angles, beginning at the corners of the square and
widening the truncation downwards, so as to give the form at _g_, where
the base of the bell is an octagon, and its top remains a square. A
very slight rounding away of the angles of the octagon at the base of
_g_ will enable it to fit the circular shaft closely enough for all
practical purposes, and this form, at _g_, is the root of nearly all
Lombardic capitals.

If, instead of a square, the head of the bell were hexagonal or
octagonal, the operation of cutting would be the same on each angle; but
there would be produced, of course, six or eight curves on the sides of
_e_, and twelve or sixteen sides to the base of _g_.

[Illustration: Fig. XXI.]

Sec. VIII. The truncations in _e_ and _g_ may of course be executed on
concave or convex forms of _d_ and _f_; but _e_ is usually worked on a
straight-sided bell, and the truncation of _g_ often becomes concave
while the bell remains straight; for this simple reason,--that the sharp
points at the angles of _g_, being somewhat difficult to cut, and easily
broken off, are usually avoided by beginning the truncation a little way
down the side of the bell, and then recovering the lost ground by a
deeper cut inwards, as here, Fig. XXI. This is the actual form of the
capitals of the balustrades of St. Mark's: it is the root of all the
Byzantine Arab capitals, and of all the most beautiful capitals in the
world, whose function is to express lightness.

Sec. IX. We have hitherto proceeded entirely on the assumption that the
form of cornice which was gathered together to produce the capital was
the root of cornices, _a_ of Fig. V. But this, it will be remembered,
was said in Sec. VI. of Chap. VI. to be especially characteristic of
southern work, and that in northern and wet climates it took the form of
a dripstone.