a moulding is so called, because of its being of the same determinate shape along its whole length, as though the whole of it had been cast in the same mould or form.

“That profile produces the happiest effect which is composed of but few members, varied in form and size, and arranged so that the plane and the curved surfaces succeed each other alternately.”

“A profile is an assemblage of essential parts and mouldings.”

MOULDINGS NAMES & USES

“Some of the terms are derived thus:

Fillet from the French word fil, thread.

Astragal from astragals, a bone of the heel—or the curvature of the heel.

Bead because this moulding, when properly carved, resembles a string of beads.

Torus or tore, the Greek for rope, which it resembles, when on the base of a column.

Scotia from shotia, [shadow] darkness, because of the strong shadow which its depth produces, and which is increased by the projection of the torus above it.

Ovolo from ovum, an egg, which this member resembles, when carved, as in the Ionic capital.

Cavetto from cavus, [cave] hollow.

Cymatium from kumaton, a wave.

—Roman mouldings are composed of parts of circles, and have, therefore, less beauty of form than the Grecian [which are composed of ovals].” Robert Griffith Hatfiel

RULES OF MOULDING ASSEMBLY

“… each one is common to all; and although each has its appropriate use, yet it is by no means confided to any certain position in an assemblage of mouldings.

The use of the fillet is to bind the parts, as also that of the astragal and torus, which resemble ropes.

The ovolo and cyma-reversa are strong at their upper extremities, and are therefore used to support projecting parts above them.

The quick turnings of the ovolo and cyma-reversa, in particular, when exposed to a bright sun, cause those narrow, well-defined streaks of light, which give life and splendour to the whole.

The cyma-recta and cavetto, being weak at their upper extremities, are not used as supporters, but are placed uppermost to cover and shelter the other parts.

The scotia is introduced in the base of a column, to separate the upper and lower torus, and to produce a pleasing variety and relief.

The form of the bead, and that of the torus, is the same; the reasons for giving distinct names to them are, that

the torus, in every order, is always considerably larger than the bead, and is placed among the base mouldings, whereas

the bead is never placed there, but on the capital or entablature;

the torus, also, is never carved, whereas the bead is; and while the torus among the Greeks is frequently elliptical in its form, the bead retains its circular shape.

While the scotia is the reverse of the torus, the cavetto is the reverse of the ovolo, and the cymarecta and cyma-reversa are combinations of the ovolo and cavetto.”

…

Robert Griffith Hatfield  The American House-Carpenter 1844