he
spur, or small buttress, sloping straight from the corner of Yb up to
the top of Xb, and as seen from above, of the shape of a triangle.
Applying such spurs in Fig. XII., we have the diagonal profile at _g_,
the perspective _h_, and the plan _i_.

Sec. XIII. I am quite sure the reader likes this last base the best,
and feels as if it were the firmest. But he must carefully distinguish
between this feeling or imagination of the eye, and the real stability
of the structure. That this real stability has been slightly increased
by the changes between _b_ and _h_, in Fig. XII., is true. There is in
the base _h_ somewhat less chance of accidental dislocation, and
somewhat greater solidity and weight. But this very slight gain of
security is of no importance whatever when compared with the general
requirements of the structure. The pillar must be _perfectly_ secure,
and more than secure, with the base _b_, or the building will be unsafe,
whatever other base you put to the pillar. The changes are made, not for
the sake of the almost inappreciable increase of security they involve,
but in order to convince the eye of the real security which the base _b_
_appears_ to compromise. This is especially the case with regard to the
props or spurs, which are absolutely useless in reality, but are of the
highest importance as an expression of safety. And this will farther
appear when we observe that they have been above quite arbitrarily
supposed to be of a triangular form. Why triangular? Why should not the
spur be made wider and stronger, so as to occupy the whole width of the
angle of the square, and to become a complete expansion of Xb to the
edge of the square? Simply because, whatever its width, it has, in
reality, no supporting power whatever; and the _expression_ of support
is greatest where it assumes a form approximating to that of the spur or
claw of an animal. We shall, however, find hereafter, that it ought
indeed to be much wider than it is in Fig. XII., where it is narrowed in
order to make its structure clearly intelligible.

Sec. XIV. If the reader chooses to consider this spur as an aesthetic
feature altogether, he is at liberty to do so, and to transfer what we
have here said of it to the beginning of Chap. XXV. I think that its
true place is here, as an _expression_ of safety, and not a means of
beauty; but I will assume only, as established, the form _e_ of Fig.
XII., which is absolutely, as a construction, easier