§ 1. I have classed these two means of architectural effect together, because the one is in most cases the negative of the other, and is used to relieve it exactly as shadow relieves light; recess alternating with roll, not only in lateral, but in successive order; not merely side by side with each other, but interrupted the one by the other in their own lines. A recess itself has properly no decoration; but its depth gives value to the decoration which flanks, encloses, or interrupts it, and the form which interrupts it best is the roll.

§ 2. I use the word roll generally for any mouldings which present to the eye somewhat the appearance of being cylindrical, and look like round rods. When upright they are in appearance, if not in fact, small shafts; and are a kind of bent shaft, even when used in archivolts and traceries;—when horizontal, they confuse themselves with cornices, and are, in fact, generally to be considered as the best means of drawing an architectural line in any direction, the soft curve of their side obtaining some shadow at nearly all times of the day, and that more tender and grateful to the eye than can be obtained either by an incision or by any other form of projection.

§ 3. Their decorative power is, however, too slight for rich work, and they frequently require, like the angle and the fillet, to be rendered interesting by subdivision or minor ornament of their own.