In practice the tranquillity of the floor zone will be disturbed by the use of a carpet or rug having a dark ground with light ornamental motives or a light ground with dark motives; by a dark rug on a light floor or a light rug on a dark floor, with the effect strikingly intensified, of course, when several small rugs are used; and by the use of light furniture and upholstery fabrics on a dark floor covering or the converse. Similarly the tranquillity of the wall zone will be disturbed by the use of very light walls with dark surbase or dado, trim, or fireplace, or the converse; or by dark hangings, pictures, cabinets or heavy chairs, or even small decorative accessories against markedly light walls, or the converse; while dark beams against a very light ceiling will have the same unesthetic result. This does not mean that tone contrasts within a given zone must be reduced to the extreme minimum; but it does mean that such contrasts must be reduced, both in number and in intensity, to the point where effects of spottiness are eliminated, and the essential tone unity of the zone is instantly apparent.
It is to be noted that contrast can give interest, zest and animation through the opposition of unlike elements either irregularly and as it were capriciously, in which case it serves merely to accent or give snap, or regularly and rhythmically, in which case the contrast itself becomes an element of unity in the composition of the room. A simple illustration is afforded by the case of blue and gold draperies. These colors contrast sharply, both in hue and tone, and when used together they are certain to give an effect of snap and animation, the intensity of the effect depending on the purity of the hues and the area of the contrasting surfaces. In a blue and gold damask or velvet these colors are combined in a repeating design, and the regular and rhythmic recurrence of the same combinations of the two hues constitutes not only a contrast, but a powerful unifying factor in the room. If on the other hand plain blue hangings are trimmed with a gold galloon, or if plain gold hangings are outlined with a gimp or fringe of blue, the contrast serves merely as an accent. Of course this plain blue fringe would in practice be made to repeat a blue in the rug, or in some other important element on or near the floor, thus serving to unify the general scheme; but so far as the hangings alone are concerned its whole function is to set off and emphasize by contrast the peculiar quality of the plain gold.
FIGURE 21.- (a) Sharp contrast, serving merely to accent and define; (b) same contrast rhythmically repeated, and therefore unifying.
In the design of rugs and furniture, as in the composition of the room as a whole, straight and curved lines are similarly combined in regular or rhythmic relationships, so that while the alternation of these lines is esthetically pleasing and stimulating, the total effect is nevertheless restful because unifying. But when these combinations of unlike outlines are not repeated or echoed-as when a round or elliptical mirror is placed between the straight supports of a straight- lined dresser or hung above a rectangular wall table or cabinet, or when a circular pillow is used on a big straight-lined davenport-no element of likeness is present and the contrast stands out in sharp relief.