the structure of piers, therefore, we shall have to see how
lintels or arches are thrown from pier to pier, and the whole prepared
for the superincumbent roof; this arrangement being universal in all
good architecture prepared for vertical pressures: and we shall then
examine the condition of the great roof itself. And because the
structure of the roof very often introduces certain lateral pressures
which have much to do with the placing of buttresses, it will be well to
do all this before we examine the nature of buttresses, and, therefore,
between parts (B) and (C) of the above plan, Sec. IV. So now we shall have
to study: (A) the construction of walls; (B) that of piers; (C) that of
lintels or arches prepared for roofing; (D) that of roofs proper; and
(E) that of buttresses.

Sec. VII. 3. _Apertures._--There must either be intervals between the
piers, of which intervals the character will be determined by that of
the piers themselves, or else doors or windows in the walls proper. And,
respecting doors or windows, we have to determine three things: first,
the proper shape of the entire aperture; secondly, the way in which it
is to be filled with valves or glass; and thirdly, the modes of
protecting it on the outside, and fitting appliances of convenience to
it, as porches or balconies. And this will be our division F; and if the
reader will have the patience to go through these six heads, which
include every possible feature of protective architecture, and to
consider the simple necessities and fitnesses of each, I will answer for
it, he shall never confound good architecture with bad any more. For, as
to architecture of position, a great part of it involves necessities of
construction with which the spectator cannot become generally
acquainted, and of the compliance with which he is therefore never
expected to judge,--as in chimneys, light-houses, &c.: and the other
forms of it are so closely connected with those of protective
architecture, that a few words in Chap. XIX. respecting staircases and
towers, will contain all with which the reader need be troubled on the
subject.

CHAPTER IV.

THE WALL BASE.

Sec. I. Our first business, then, is with Wall, and to find out wherein
lies the true excellence of the "Wittiest Partition." For it is rather
strange that, often as we speak of a "dead" wall, and that with
considerable disgust, we have not often, since Snout's time, heard of a
living one. But the comm