Chap. XXXI.
PRINCIPLES OF PROPORTION.
1599
triumphal arches with a single opening, though varying materially from the principleslaid down by Poliphele, and adopted by Serlio and other architects at the revival of Italian
architecture. The Arch t ..... . . _ . --
of Titus is a square com- r— - - —~ ~L
prising its entire fa 9 ade ; ■- 1 - ~ L ~
that of Poliphele a squareup to the under side ofthe entablature; conse-quently, the opening ofthe triumphal way is inwidth half the heightto the top of the impostupon which the archivoltrests, while in the moreancient the entire aper-ture without the arch isa square.
In the Arch of Poli-phele the entablature andpediments are nearlyequal in quantity to eachof the piers upon whichthey are carried; and thepiers themselves are inwidth only one quarter ofthe whole breadth of thefa 9 ade: it will be found,however, that nearly thesame proportions exist be-tween supports and sup-ported in both examples.
The Arch of Augustus at Susa has a singlearch: proportion a squareto the top of the entabla- Fig- 2995.ture, opening a square to the springing: width divided into four, two given to the openingand one to each pier, which has a three-quarter column at the angle: attic as high as piersare wide.
In arches with three openings, as those of Septimus Severus and Constantine, these
I
ARCH OF AUGUSTUS AT SUSA.
Fig. 2996.