I presume that the occurrence of a number of simple ornamental elements may be explained as technically determined. We have seen before that the straight line and the regular curve such as circle and spiral presuppose an accurate technique, that they are too rare in nature to be considered as representative in character. The straight line may be the result of cutting, folding or splitting some kinds of wood, of the use of reeds or similar materials, of stretching fibres and of many other processes. Circles may originate by the regular turning of coiled basketry and of coiled pottery: spirals by the laying of coarse coils. Weaving in coarse material leads to rectangular figures, to checker patterns, steplike diagonals and to many other complicated forms. Tying with cord produces straight lines intersecting at various angles and also parallel, circular and spiral forms. We may confidently claim independent origin in separate areas for the triangular design in basketry (fig. 104 _a_, _b_, p. 109); for simple radial forms in coiled basketry placques; for the swastika cross, the meander and for many other simple forms, like the spirals of prehistoric Bohemia; of eastern Siberia; of Melanesia and of ancient New Mexico; in the sameness of design elements from Africa and America; in the occurrence of the circle and central dot in prehistoric Europe and among the Eskimo. The principle of symmetry, of balance, of rhythmic repetition and of emphasis laid upon prominent points or lines apply to all kinds of technique and many lead to parallel developments. We have seen that in some cases, simple elements which develop independently, possess stylistic peculiarities that differentiate one locality from another. But even if the forms are identical, the arrangement in the decorative field is liable to give a specific form to the art of each locality. The negroes of the Congo present an excellent example of the transfer of design from one technique to another. Their woven patterns consist largely of intersecting bands, imitating the interweaving of broad bands. These motives appear in most of the decorative work of these tribes. Their embroidered pile cloth (fig. 133) imitates the interwoven patterns; they reappear on their wood carvings, particularly on their goblets (see fig. 52, p. 59), and on carvings on buffalo horns. [Illustration: Fig. 133. Pile cloth, Congo.] Interwoven bands that look like imitations of coarse weaving are also very common in American art. They are found in many parts of South America and among the Pueblo Indians. Some of the wood carving of Tonga is evidently influenced in style by the artistic methods of tying, which are highly developed in the islands of the Pacific Ocean.