Ionic Archivolt
The archivolt, commencing at the outer rim, consists of a fillet and bold reversa moulding which occupies rather less than a fourth of the total width, and two facias of unequal widths. The width of the inner facia is nearly one-third more than that of the reversa moulding.
Corinthian Impost
The Corinthian impost differs from those of the other two orders in having a necking and necking moulding in place of the two unequal facias.
The total height should be divided into two, and the upper half divided into four. Then the top fillet and reversa moulding will be one of these divisions, the facia two, and the supporting ovolo will occupy the remaining one.
The lower half of the impost consists of a small torus and fillet beneath the ovolo, the necking, and the torus and fillet which form the necking moulding.
Corinthian Archivolt
The archivolt, commencing at the outer rim, consists of a fillet and reversa and three unequal facias.
If the total width is divided into two, the point of bisection will be the centre of a small reversa moulding between the two outer facias. The outer reversa and the inner facia are each about one-sixth of the total width and the small reversa is about two-thirds of the inner facia.