Encyclopaedia Britannica > Volume 3, Anatomy-Astronomy

arch.
strictest manner. We are sometimes disposed to think
that the painted glass (a fashion brought from the East)
was an imitation of the painted hangings of the Arabs.
6. The Chinese architecture is an evident imitation of
a wooden building. Sir George Staunton says, that the
singular form of their roofs is a professed imitation of the
cover of a square tent.
In the stone buildings of the Greeks, the roofs were imi¬
tations of the wooden ones ; hence the lintels, flying cor¬
nices, ceilings in compartments, &c.
7. Ihe pediment of the Greeks seems to have suggested
the greatest improvement in the art of building. In erect¬
ing their small houses, they could hardly fail to observe
occasionally, that when two rafters were laid together
from the opposite walls, they would, by leaning on each
other, give mutual support,as in Plate XLVIII.fig. 1. Nor is
it unlikely that such a situation of stones as is represented
in fig. 2 would not unfrequently occur by accident to ma¬
sons. This could hardly fail of exciting a little attention
and reflection. It was a pretty obvious reflection, that
the stones A and C, by overhanging, leaned against the
intermediate stone B, and gave it some support, and that
B cannot get down without thrusting aside A and C, or
the piers which support them. This was an approach to
the theory of an arch; and if this be combined with the
observation of fig. 1, wre get the disposition represented in
fig. 3, having a perpendicular joint in the middle, and the
principle of the arch is completed. Observe that this is
quite different from the principle of the arrangement in
fig. 2. In that figure the stones act as wedges, and one
cannot get down without thrusting the rest aside. The
same principle obtains in fig. 4, consisting of five arch¬
stones ; but in fig. 3 the stones B and C support each other
by their mutual pressure (independent of their own
weight), arising from the tendency of each lateral pair to
fall outwards from the pier. This is the principle of the
arch, and would support the key-stone of fig. 4, although
each of its joints were perpendicular, by reason of the
great friction arising from the horizontal thrust exerted
by the adjoining stones.
This was a most important discovery in the art of build¬
ing ; for now a building of any width may be roofed with
stone.
8. We are disposed to give the Greeks the merit of this
discovery; for we observe arches in the most ancient
buildings of Greece, such as the temple of the sun at
Athens, and of Apollo at Didymos—not indeed as roofs
to any apartment, nor as parts of the ornamental design,
but concealed in the walls, covering drains ci other neces¬
sary openings ; and we have not found any real arches in
any monuments of ancient Persia or Egypt. Sir John
Chardin speaks of numerous and extensive subterranean
passages at Tchelminar, built of the most exquisite ma-
sonry, the joints so exact, and the stones so beautifully
dressed, that they look like one continued piece of polish¬
ed marble ; but he nowhere says that they are arched—a
circumstance which we think he would not have omitted:
no arched door or window is to be seen. Indeed one of
the tombs is said to be arch-roofed, but it is all of one
solid rock. No trace of an arch is to be seen in the ruins of
ancient Egypt; even a wide room is covered with a single
block of stone. In the pyramids, indeed, there are two gal¬
leries whose roofs consist of many pieces ; but their construc¬
tion puts it beyond doubt that the builder did not know what
an arch was ; for it is covered in the manner represented in
ii • *’ )♦' ^ every Projecting piece is more than balanced
behind, i et there are perfect arches, both circular and
pointed, in the pyramidal remains at Djebel-el-Berkel, the
ancient Napata, in Meroe, the cradle of Egyptian art. The
arched dome, however, seems to have arisen in Etruria,
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401
and originated in all probability from the employment of Arch,
the augurs, whose business it was to observe the flight of'—
Uiij Their stations for this purpose were templa, so
called a templando, on the summits of hills. To shel¬
ter such a person from the weather, and at the same time
allow him a full prospect of the country around him, no
building was so proper as a dome set on columns; which
accordingly is the figure of a temple in the most ancient
monuments of that country. We do not recollect a build¬
ing of this kind in Greece except that called the Lanthom
of Demosthenes, but this is covered by a single stone. In
the later monuments and coins of Italy or of Rome we com¬
monly find the Etruscan dome and the Grecian temple com¬
bined ; and the famous Pantheon was of this form, even in
its most ancient state.
9. It does not appear that the arch was considered as a
part of the ornamental architecture of the Greeks during
the time of their independency. It is even doubtful whe^
ther it was employed in roofing their temples. In none
of the ancient buildings where the roof is gone can there
be seen any rubbish of the vault or mark of the spring of
the arch. It is not unfrequent, however, after the Roman
conquests, and may be seen in Athens, Delos, Palmyra,
Balbeck, and other places. It is very frequent in the
magnificent buildings of Rome ; such as the Coliseum, the
baths of Diocletian, and the triumphal arches, where its
form is evidently made the object of attention. But its
chief employment was in bridges and aqueducts; and it
is in these works that its immense utility is the most con¬
spicuous : for by this happy contrivance a canal or a road
may be carried across any stream, where it would be al¬
most impossible to erect piers sufficiently near to each
other for carrying lintels. Arches have been executed
130 feet wide, and their execution demonstrates that they
may be made four times as wide.
10. As such stupendous arches are the greatest per¬
formances of the masonic art, so they are the most diffi¬
cult and delicate. When we reflect on the immense
quantity of materials thus suspended in the air, and com¬
pare this with the small cohesion which the firmest ce¬
ment can give to a building, we shall be convinced that it
is not by the force of the cement that they are kept to¬
gether ; they stand fast only in consequence of the proper
balance of all their parts. Therefore, in order to erect
them with a well-founded confidence of their durability,
this balance should be well understood and judiciously
enqfloyed. We doubt not but that this was understood
in some degree by the engineers of antiquity; but they
have left us none of their knowledge. They must have
had a great deal of mechanical knowledge before they
could erect the magnificent and beautiful buildings whose
ruins still enchant the world; but they kept it among
themselves. We know that the Dionysiacs of Ionia were
a great corporation of architects and engineers, who un¬
dertook and even monopolized the building of temples,
stadiums, and theatres, precise!}' as the fraternity of ma¬
sons in the middle ages monopolized the building of ca¬
thedrals and conventual churches. Indeed the Dionysiacs
resembled the mystical fraternity now called free-masons
in many important particulars. They allowed no strangers
to interfere in their employment; they recognised each
other by signs and tokens; they professed certain myste¬
rious doctrines, under the tuition and tutelage of Bac¬
chus, to whom they built a magnificent temple at Teos,
where they celebrated his mysteries as solemn festivals ;
and they called all other men profane because not admit¬
ted to these mysteries. But their chief mysteries and
most important secrets seem to be their mechanical and
mathematical sciences, or all that academical knowledge
which forms the regular education of a civil engineer.
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