Riou, Stephen: The Grecian orders of architecture: delineated and explained from the antiquities of Athens ; also the parallels of the orders of Palladio, Scamozzi and Vignola (London, 1768)

2 2 The Grecian Orders
The (ydyle may have the height of its columns nine diameters and a hals.
In the pyenostyle the columns are prescribed at ten diameters in height. These two last inter-
columniations are adapted to the Corinthian.
The reason of these disferent proportions is, because the sree passage os air between the inter-
vals of columns, doth as it were consume and diminish the thickness os columns, and the more
air and light do sur round them, the more ssender do columns appear; theresore the angular co-
lumns have been allowed to have their diameters increased one fiftieth part more than the inter-
vening ones.
The wider intercolumniations will admit of columns being disposed by couplets; they are
then placed two by two with surhcient spaces sor the presectures of their capitals and bases; and re-
gard also muss be had to the triglyphs, mutules, dentels, and modilions of their respective
cornices. By this dtspoiition of couplets, the angles of a building seem to be greatly
(lengthened ; but it gives a crowded and irregular aspect in the center os an edisice.
Columns in the fore and back front are generally disposed in an even number, otherwise the
middle of the front would present a column instead of a vacuity for a door-way, and then it would
require two door-ways; besides, the architrave considered as a beam with a weight suspended
in its middle, ;". e. the center of gravity, demands the same number of men (their slxength
supposed to be equal) on one side as on the other to bear it up.
The diminution of the ssiafts of columns upwards, gives a gracesulness to their sorms, which
otherwise they would want. But the swelling in the middle can convey no other idea than that
of the columns being oppressed by the incumbent weight. The remains os antiquity cannot
furnish examples of the latter practice. Sir H. Wotton condemns it as a great ablurdity.
Some authors with Vitruvius, as above quoted, have decided, that columns os disserent altitudes
require different diminutions, but to judge from the remains of antiquity, this precept seems not to
have been scrupulousiy practised, for neither the very lofty columns of the temple os Fauftina, nor
those of the portico os Septimius, of the temple of Concord, and os the baths os Diocletian
have more diminution than others os hals their height, as those of the triumphal arches os Titus,
os Septimius, and of Constantine.
The disserent characters of the orders, have been judged to require disserent diminutions os
their (hasts; we sind authority sor this in the antiquities os Athens, which correspond nearly
with the rules established by Scamozzi.
For the Doric column, the top os the (hast is four fisths os the diameter at bottom.
For the Ionic column, the diminution is one seventh.
For the Corinthian column, the lhast at top is seven-eighths os the diameter at bottom.
Vignola and others make the (hasts os every order to diminish only one sixth, and this gene-
ral diminution may in common cases be received with great propriety.
To begin the diminution srom the bottom os the (hast, is the moil natural and mod ap-
proved, cfpecially sor the Doric, but sor the Ionic and Corinthian orders, the diminution may
begin at one-third os the length os the (hast; it is thus traced sor the column A. B. From the
point E. describc the semi-circle E. D. C. &c. srom A. the point os diminution at-top, let sall
the perpendicular A. G. divide the arch G. E. into several equal parts at pleasure; e.g. into
six, and raise so many perpendiculars, divide E. A. into the same equal number os parts, and
through the points os interse&ion, E, H. L. K, L. M. A. trace the line that will give the sur-
sace