Civil Engineering Reference
In-Depth Information
the Romans used ashlar masonry construction (
opus saxum, opus
quadratum
), the
i neness of jointing deteriorated. Above all they began to be more concerned with
aspect than structural solidarity. h e greatest possible visual ef ect was sought from
i ne dressing, thus more and more blocks were set so that the surface of the greatest
area was the face rather than the bed. h is attitude culminated in the practice of
revetting walls with marble facing slabs, which gave an impressive aspect but added
no solidity to the construction. Martin pp. 445-447 of ers a nuse en seene of this
development, which is the basis of the statement of Augustus that he found Rome
brick and let it marble (Vol. 1 p. 113, ill 45; Vol. 2 p. 68, ills 106, 110, 111).
Optical
rei ne-
ments
205
204, 206
EXCURSUS. OPTICAL REFINEMENTS
By the latter part of the 19th century it was universally recognised that some of the
superb religious monuments of Classical Greek architecture incorporated subtle
rei nements of design. Although the adjustments in form involved were very slight,
by careful mensuration with optical instruments they could be recorded and objec-
tively established. h e upshot of these adjustments was that some straight lines were
transformed into slight convex curves and some verticals were given a slight inward
inclination. Much discussion ensued concerning the rationale of these measures—and
it was agreed that their ef ect was to impart a “life” to the structure which was lacking
in a mechanical rectiliniarity. Also it was reckoned that these adjustments “corrected”
three dimensional appearances brought about by the modalities of vision (optics) (cf
Lawrence, Chap. 15, pp. 169-75).
h ese recondite matters pertain to design and are outside the concern of the
present study. However it must be noted that virtually no discussion exists on how
the “optical rei nements” were worked into the masonry construction. h e slightest
consideration of this matter indicates that they must have occasioned very dii cult
additional problems and processes to the masonry work. h is subject is too uncertain
and far reaching to be taken up here. Only it may be observed that the overall ef ect in
some instances was to create a curious parallel with the normal process of Pharaonic
Egyptian masonry—i.e. the comprehending masonry mass was built up and then the
i nished lines of the structure were “carved out” of this mass
in situ
. In this connection
it is also possible to make a further observation. It is always understood that these opti-
cal rei nements are absolutely specii c to Classical Greek ashlar masonry. Nonetheless
there have been hints that something similar is found in Pharaonic masonry. Whereas
the peripheral lines of the base of a Greek temple (the stylobate) are given a slight
(upward) convex curve in elevation, it has been asserted that the peripheral lines of
the base of an Egyptian temple are on occasion given a slight (outward) convex curve
in plan. h is is a question that is in no way settled and awaits further investigation.
Only it may be noted that if a three dimensional drawing is made to illustrate (by exag-
geration) the ef ects of Greek optical rei nements, the eye has dii culty determining
whether the convex curves of the stylobate are upwards or outwards, (Vol. 1, ill 34).
233
Coursed orthogonal ashlar (isodomic or pseudo-isodomic) was not the only type
of i nely dressed stone masonry used in Classical Greek construction. Two or three
