forms, surfaces, and textures. The simplest
illustrations of the principles of modelled relief are to be found in
architectural mouldings, by means of which buildings are relieved and
enriched, and important structural or functional parts are emphasized,
as in cornices and ribs of vaults, arches, and openings.

Place a concave moulding side by side with a convex one either
horizontally or vertically, and a certain pleasant effect of contrasting
light and shade is the result, reminding one of the recurring concave
and convex of the rolling waves of the sea (A, p. 191[f104]).

A series of flat planes of different widths and at different levels also
produces a pleasant kind of relief useful in a picture frame or the jamb
of a door (B).

All architectural mouldings might be said to be modifications or
combinations of the principles illustrated by these two.

Very different feeling may be expressed in mouldings, and if we compare
the two types, the classical and the Gothic, the comparatively broad and
simple effect of the former (C, D, E, F, G) contrasts with the
richness and variety and the stronger effect of light and shade,
produced by deep undercutting, in the latter (H, I, J, K).

[Illustration (f104): Relief in Architectural Mouldings.]

The Romans, however, produced rich and highly ornate effects in the use
of these types of mouldings, as they reappeared in the Corinthian order,
the ovolo cut into the egg and dart, with the Astralagus beneath, the
Cyma recta above the brackets of the cornice casting a bold shadow, and
both in the cornice and the hollow beneath the dentils enriched with
carving, as seen in the splendid fragment of the Forum of Nerva.

[Illustration (f105): Roman Treatment of Corinthian Order, Forum of
Nerva, Rome.]

When we pass to the more complex problems of figure modelling and
sculpture, it is but carrying on and developing the same principle of
the contrast of planes, of the relief of plane upon plane, of forms upon
one plane, to forms upon forms in many planes. From the contrast of bead
and hollow we come to consider the contrast between the rounded limb and
the sinuous folds of drapery; from the rhythm of the acanthus scroll we
turn to the less obvious but none the less existing rhythm of the
sculptural frieze.

Line, we may say, controls the modeller's and sculptor's composition,
but form and its treatment in light and shade give him his means of
ornament. The delicate contours of fac