The birchbark basketry of western North America and of Siberia presents an excellent example of a marginal pattern originating through technical necessity and regularity of motor habits. Necessary protection of the rim is obtained by sewing on a hoop. The grain of the bark runs parallel to the rim and if the stitches were all passing through the same grain the whole rim of the basket would tear off. It is therefore necessary to make the holding stitches of different lengths. This is done in the most effective way by beginning with a short stitch which passes through the bark immediately under the strengthening hoop, by making the next stitch a little longer and the following still longer. In this way the distance from the first short stitch has become long enough to permit a repetition of the new short stitch and by continuing in this way a marginal pattern of right triangles develops. The same result may be attained by alternating a few short stitches with a few long ones. From this results a different type of pattern. The same method is used by the Golds of southeastern Siberia (fig. 49[39]). [39] See for a fuller description the remarks by F. Boas in James Teit “The Shuswap”, Publications of the Jesup North Pacific expedition, Volume II, page 478-487. [Illustration: Fig. 50. Pottery vessels; _a_, _b_, Chiriqui, Costa Rica; _c_ Ontario.] In woodwork, pottery and in most kinds of metal work these technical motives are not present. Nevertheless marginal patterns are widely distributed, although they cannot be explained on the basis of technical considerations. It would be quite arbitrary to claim that all these marginal patterns were primarily suggested in those types of technique in which a distinctive treatment of the margin is a necessity, for these are relatively few in number and of highly specialized character, while rim patterns are well nigh universal. It is instructive to observe that in coiled pottery the whole body of the vessel is generally polished off and that sometimes the impressions of the modelling fingers are left on the rim. There is no technical, compelling reason that requires this mode of treatment, but it is intelligible as an attempt to emphasize the form. Examples of this mode of treatment are very numerous. Rows of small pellets, moulded rims or incised lines along the rim of pots (fig. 50), small marginal curves along the rim of bronze disks, lines accompanying the rims of flat dishes and spoons such as are used by the Alaskan Eskimo, incised lines on the rim of a soapstone pot of the Hudson Bay Eskimo, and on their ivory combs (fig. 51), the spur line decoration of all the Eskimo tribes (see fig. 78, p. 86), the jutting out of the rims of dishes from Oceania, or on pots from ancient Europe are of this kind. As F. Adama van Scheltema has justly pointed out, we cannot reduce this world-wide tendency to any other ultimate cause than to a feeling for form, in