, stronger, and more
perfect than _b_. A word or two now of its materials. The wall base, it
will be remembered, was built of stones more neatly cut as they were
higher in place; and the members, Y and X, of the pier base, were the
highest members of the wall base gathered. But, exactly in proportion to
this gathering or concentration in form, should, if possible, be the
gathering or concentration of substance. For as the whole weight of the
building is now to rest upon few and limited spaces, it is of the
greater importance that it should be there received by solid masonry. Xb
and Yb are therefore, if possible, to be each of a single stone; or,
when the shaft is small, both cut out of one block, and especially if
spurs are to be added to Xb. The reader must not be angry with me for
stating things so self-evident, for these are all necessary steps in the
chain of argument which I must not break. Even this change from detached
stones to a single block is not without significance; for it is part of
the real service and value of the member Yb to provide for the reception
of the shaft a surface free from joints; and the eye always conceives it
as a firm covering over all inequalities or fissures in the smaller
masonry of the floor.

Sec. XV. I have said nothing yet of the proportion of the height of Yb to
its width, nor of that of Yb and Xb to each other. Both depend much on
the height of shaft, and are besides variable within certain limits, at
the architect's discretion. But the limits of the height of Yb may be
thus generally stated. If it looks so thin as that the weight of the
column above might break it, it is too low; and if it is higher than its
own width, it is too high. The utmost admissible height is that of a
cubic block; for if it ever become higher than it is wide, it becomes
itself a part of a pier, and not the base of one.

Sec. XVI. I have also supposed Yb, when expanded from beneath Xb, as
always expanded into a square, and four spurs only to be added at the
angles. But Yb may be expanded into a pentagon, hexagon, or polygon; and
Xb then may have five, six, or many spurs. In proportion, however, as
the sides increase in number, the spurs become shorter and less energetic
in their effect, and the square is in most cases the best form.

Sec. XVII. We have hitherto conducted the argument entirely on the
supposition of the pillars being numerous, and in a range. Suppose,
however, that we require only a singl