the necessary result of the broad curve of the
arch itself, that there is no structural necessity of elevating the
jamb; and I believe that beautiful entrances might be made of every span
of arch, retaining the jamb at a little more than a man's height, until
the sweep of the curves became so vast that the small vertical line
became a part of them, and one entered into the temple as under a great
rainbow.

Sec. VIII. On the other hand, the jamb _may_ be elevated indefinitely, so
that the increasing entrance retains _at least_ the proportion of width
it had originally; say 4 ft. by 7 ft. 5 in. But a less proportion of
width than this has always a meagre, inhospitable, and ungainly look
except in military architecture, where the narrowness of the entrance is
necessary, and its height adds to its grandeur, as between the entrance
towers of our British castles. This law however, observe, applies only
to true doors, not to the arches of porches, which may be of any
proportion, as of any number, being in fact intercolumniations, not
doors; as in the noble example of the west front of Peterborough, which,
in spite of the destructive absurdity of its central arch being the
narrowest, would still, if the paltry porter's lodge, or gatehouse, or
turnpike, or whatever it is, were knocked out of the middle of it, be
the noblest west front in England.

Sec. IX. Further, and finally. In proportion to the height and size of the
building, and therefore to the size of its doors, will be the thickness
of its walls, especially at the foundation, that is to say, beside the
doors; and also in proportion to the numbers of a crowd will be the
unruliness and pressure of it. Hence, partly in necessity and partly in
prudence, the splaying or chamfering of the jamb of the larger door will
be deepened, and, if possible, made at a larger angle for the large door
than for the small one; so that the large door will always be
encompassed by a visible breadth of jamb proportioned to its own
magnitude. The decorative value of this feature we shall see hereafter.

Sec. X. The second kind of apertures we have to examine are those of
windows.

Window apertures are mainly of two kinds; those for outlook, and those
for inlet of light, many being for both purposes, and either purpose, or
both, combined in military architecture with those of offence and
defence. But all window apertures, as compared with door apertures, have
almost infinite licence of form