e
should be left as possible of its being thrown off its balance. It will
therefore be prudent to leave it slightly thicker at the base than at
the top. This excess of diameter at the base being determined, the
reader is to ask himself how most easily and simply to smooth the
column from one extremity to the other. To cut it into a true
straight-sided cone would be a matter of much trouble and nicety, and
would incur the continual risk of chipping into it too deep. Why not
leave some room for a chance stroke, work it slightly, _very_ slightly
convex, and smooth the curve by the eye between the two extremities? you
will save much trouble and time, and the shaft will be all the stronger.

[Illustration: Fig. XIII.]

This is accordingly the natural form of a detached block shaft. It is
the best. No other will ever be so agreeable to the mind or eye. I do
not mean that it is not capable of more refined execution, or of the
application of some of the laws of aesthetic beauty, but that it is the
best recipient of execution and subject of law; better in either case
than if you had taken more pains, and cut it straight.

Sec. IV. You will observe, however, that the convexity is to be very
slight, and that the shaft is not to _bulge_ in the centre, but to taper
from the root in a curved line; the peculiar character of the curve you
will discern better by exaggerating, in a diagram, the conditions of its
sculpture.

Let _a_, _a_, _b_, _b_, at A, Fig. XIII., be the rough block of the
shaft, laid on the ground; and as thick as you can by any chance require
it to be; you will leave it of this full thickness at its base at A, but
at the other end you will mark off upon it the diameter _c_, _d_, which
you intend it to have at the summit; you will then take your mallet and
chisel, and working from _c_ and _d_ you will roughly knock off the
corners, shaded in the figure, so as to reduce the shaft to the figure
described by the inside lines in A and the outside lines in B; you then
proceed to smooth it, you chisel away the shaded parts in B, and leave
your finished shaft of the form of the _inside_ lines _e_, _g_, _f_,
_h_.

The result of this operation will be of course that the shaft tapers
faster towards the top than it does near the ground. Observe this
carefully; it is a point of great future importance.

Sec. V. So far of the shape of detached or block shafts. We can carry the
type no farther on merely structural considerati