Civil Engineering Reference
In-Depth Information
ii. h e Dome
h e historical development of the domical form does not begin underground.
A very early (Mesolithic—Neolithic) form of shelter was the “round house”, a
beehive cavern in form. Originally built of pliable vegetal materials, during the
early (Pre Pottery) Neolithic Period it was constructed in solid mud brick or mud
brick and rubble—thus the domical form appeared i rst in materials other than
stone. Pharaonic Egyptian stone building never accepted the round plan. Egyptian
planning remained entirely rectilinear, so that the stone dome never ocurred as a
building form in Ancient Egypt.
h e stone dome made its appearance in underground built tombs of the Bronze
Age Levant and swit ly developed into monumental form during the Late Bronze
Age as the h olos Tomb of Mycenaean Greece (v
supra
, pp. 179, 180). h e masonry
construction was horizontally coursed corbelling, but since the chamber was bur-
ied within an earth tumulus the surrounding earth exercised the inward pressure
necessary to restrain any deformation by outward thrust, so that the assemblage
functioned as a “true” dome—i.e. the component blocks of each course (or 'par-
allel') were held in compression. However with the downfall of the Mycenaean
civilisation, this genre of corbelled domical construction disappeared in Greece.
On the other hand, in a way not easy to account for tumulus tomb chambers
similar to the Mycenaean tholoi occured during the mid i rst millenium BC in
various regions under Greek inl uence—Etruria in the West and the Pontic region
(h race and the Crimea) in the East. Moreover these corbelled beehive chambers
show a formal development over the Mycenaean h oloi, which they resemble in
essentials. Not only were the beehive domes raised over circular chambers, but they
were also constructed over square chambers. Here the transition from the square
plan was made by corbelled out arcs of masonry set in the angles. h ese devices
were designed and functioned in exactly the same manner as the spherical triangle
pendentives of the 'true' masonry domes constructed with radially set voussoirs
half a millenium later (v
infra
, pp. 191, 192). An extended résumé account of
these beehive domed tumulus tombs is given in Orlandos 2, pp. 201-17.
At all events when during the latter part of the 4th century BC Greek build-
ers began to build arches and vaults from radially bedded voussoirs, they did not
likewise dress voussoirs for building domes. h is development did not take place
for another 300 years, and then all the surviving evidence indicates that the earliest
dressed stone domes were built in the heartland of Oriental Hellenism—Palestine,
Syria, Southern Anatolia—not in Greece. For this fact no convincing explanation
is readily available.
In considering the Graeco-Roman ashlar stone dome there are two distinct
structural questions at issue, i.e. a second issue over and above matters relating
equally to the vault. h ere is the question of the form and setting of the vous-
soirs composing the dome proper as a parallel issue to the form and setting of
Arcuated
stone
rooi ng—
the Dome
280, 281
284
285, 289
290
291-293
290
298
298
