s of London; or
of hewn stone, in stronger work; or in a single sloping face, inclined
to the outside. We need not trouble ourselves at present about these
small roofings, which are merely the diminutions of large ones; but we
must examine the important and constant member of the wall structure,
which prepares it either for these small roofs or for weights above, and
is its true cornice.

Sec. II. The reader will, perhaps, as heretofore, be kind enough to think
for himself, how, having carried up his wall veil as high as it may be
needed, he will set about protecting it from weather, or preparing it
for weight. Let him imagine the top of the unfinished wall, as it would
be seen from above with all the joints, perhaps uncemented, or
imperfectly filled up with cement, open to the sky; and small broken
materials filling gaps between large ones, and leaving cavities ready
for the rain to soak into, and loosen and dissolve the cement, and
split, as it froze, the whole to pieces. I am much mistaken if his
first impulse would not be to take a great flat stone and lay it on the
top; or rather a series of such, side by side, projecting well over the
edge of the wall veil. If, also, he proposed to lay a weight (as, for
instance, the end of a beam) on the wall, he would feel at once that the
pressure of this beam on, or rather among, the small stones of the wall
veil, might very possibly dislodge or disarrange some of them; and the
first impulse would be, in this case, also to lay a large flat stone on
the top of all to receive the beam, or any other weight, and distribute
it equally among the small stones below, as at _a_, Fig. IV.

[Illustration: Fig. IV.]

Sec. III. We must therefore have our flat stone in either case; and let
_b_, Fig. IV., be the section or side of it, as it is set across the
wall. Now, evidently, if by any chance this weight happen to be thrown
more on the edges of this stone than the centre, there will be a chance
of these edges breaking off. Had we not better, therefore, put another
stone, sloped off to the wall, beneath the projecting one, as at _c_.
But now our cornice looks somewhat too heavy for the wall; and as the
upper stone is evidently of needless thickness, we will thin it
somewhat, and we have the form _d_. Now observe: the lower or bevelled
stone here at _d_ corresponds to _d_ in the base (Fig. II., page 59).
That was the foot of the wall; this is its hand. And the top stone here,
which is a