The Arch
In
view of the fact that some writers have
claimed that the principle of the arch was
not known until long after Solomon’s time
and that therefore the keystone could not
have been used in the Temple, consider the
following article from the Encyclopaedia
Britannica:
ARCH, any combination
of blocks of building material, generally
wedge-shaped and with radial joints,
employed to cap an opening wider than any of
the blocks themselves capping it. In form,
arches are usually, though not always, built
with the soffit following a curved line. By
extension, the word arch is used for any
curved head of an opening or recess, even
when the material is homogeneous, as in a
concrete arch. From the use of arch forms,
to bridge the spaces between the beams in
early fireproof construction, the word arch
is employed technically for any structure
between steel beams, even when the structure
may be of reinforced concrete, and,
therefore, theoretically a beam, and not an
arch at all.
In the normal arch,
the inside face or soffit is known as the
intrados, the outside face as the extrados,
the wedge- shaped blocks as voussoirs, the
centre voussoir as the keystone and the two
end voussoirs as the springers. The spring
of the arch is the level of the bottom of
the springers, which usually coincides with
the beginning of the curvature, but a
stilted arch is one in which the apparent
spring is well below this beginning. The
haunches of an arch are the parts between
keystone and springer. A continuous arch,
such as a tunnel, is known as a vault.
Due to the nature of
its construction, with wedge-shaped blocks,
any arch exerts at its spring, not only a
downward weight, but a tendency to spread
which is known as thrust, and for the arch
to remain stable it is necessary for this
thrust to be resisted adequately by
abutments, buttresses or the strength of the
wall itself in which the arch is placed.
This quality of exerting thrust has
profoundly affected architecture.
The principle of the
arch has been known from very early times.
When neolithic man discovered that a wide
opening could be spanned by leaning two
stones together at its apex, the first arch
was made, and such triangular arches are
widely found throughout the Mediterranean
basin (for example, one at Alea in Arcadia;
a similar triangular shape, though in
corbelled construction is seen in the Gate
of the Lions at Mycenae). The earliest known
developed arches with curved sides occur in
the Tigre-Euphrates valley, at least as
early as 4000 BC In Egypt, also the arch was
known, although it was used only for
utilitarian purposes. Almost all of these
early examples are over drains, where the
abutment question was simple, but in Asia,
the Assyrians, at least, used the arch
monumentally in gateways. It was, however,
in Italy, at the hands of the Etruscans,
that the arch received its most important
early architectural treatment, as in the
famous gate of Perugia. Following the
Etruscans the Romans adopted the arch as
perhaps the chief structural feature in the
design of monumental buildings and by them
its use was spread all over the civilized
world to become an integral feature of all
the architecture succeeding them until the
middle of the 19th century. Since
that time the discovery of the fact that
iron, and later steel, could be formed into
beams of great strength over long spans has
reduced the use of the arch to a subsidiary
and often merely decorative position.
|