Jackson, Thomas Graham, Sir, 1835-1924 · Cambridge, University Press · leaf 248
ptingthe brick cornices. Arches across the gallery in the lineof the angle buttresses support the central drum andvault, which is also steadied by the weight of the wallsthat are carried up and enclose the cupola. There is inthis construction something approaching that by equi-librium of forces… … \ I I ALI , KA\ L.NAA CH. xiij RAVENNA, THE EXARCHATE 177 but the construction seems to have required further support, s. Vitaiefor at some time flying buttresses have been constructedagainst two of the exterior angles of the octagon. The exterior of the semi-circular apse is polygonal. The…
