m the Gothic of almost every
period, as well as for many other faults and mistakes: no Gothic
school having ever been thoroughly systematised or perfected, even
in its best times. But that a mistaken decoration sometimes occurs
among a crowd of noble ones, is no more an excuse for the
habitual--far less, the exclusive--use of such a decoration, than
the accidental or seeming misconstructions of a Greek chorus are an
excuse for a school boy's ungrammatical exercise.

CHAPTER XV.

THE BUTTRESS.

Sec. I. We have hitherto supposed ourselves concerned with the support
of vertical pressure only; and the arch and roof have been considered as
forms of abstract strength, without reference to the means by which
their lateral pressure was to be resisted. Few readers will need now to
be reminded, that every arch or gable not tied at its base by beams or
bars, exercises a lateral pressure upon the walls which sustain
it,--pressure which may, indeed, be met and sustained by increasing the
thickness of the wall or vertical piers, and which is in reality thus
met in most Italian buildings, but may, with less expenditure of
material, and with (perhaps) more graceful effect, be met by some
particular application of the provisions against lateral pressure called
Buttresses. These, therefore, we are next to examine.

Sec. II. Buttresses are of many kinds, according to the character and
direction of the lateral forces they are intended to resist. But their
first broad division is into buttresses which meet and break the force
before it arrives at the wall, and buttresses which stand on the lee
side of the wall, and prop it against the force.

The lateral forces which walls have to sustain are of three distinct
kinds: dead weight, as of masonry or still water; moving weight, as of
wind or running water; and sudden concussion, as of earthquakes,
explosions, &c.

Clearly, dead weight can only be resisted by the buttress acting as a
prop; for a buttress on the side of, or towards the weight, would only
add to its effect. This, then, forms the first great class of buttressed
architecture; lateral thrusts, of roofing or arches, being met by props
of masonry outside--the thrust from within, the prop without; or the
crushing force of water on a ship's side met by its cross timbers--the
thrust here from without the wall, the prop within.

Moving weight may, of course, be resisted by the prop on the lee s