To sum up: Objectively the excellence of workmanship results in regularity of form and evenness of surface which are characteristic of most uncontaminated primitive manufactures, so much so that most objects of every day use must be considered as works of art. The handles of implements, stone blades, receptacles, clothing, permanent houses, canoes are finished off in such a way that their forms have artistic value. [Illustration: Fig. 18. Carving on bow of Bella Bella canoe, British Columbia.] [Illustration: Fig. 19. Rattle, Kwakiutl Indians, British Columbia.] Expert workmanship in the treatment of the surface may lead not only to evenness but also to the development of patterns. In adzing the form of the object to be smoothed will determine the most advantageous direction of the lines in which the adze has to be carried. In a large Bella Bella canoe, the body of the canoe is adzed in horizontal lines, while prow and stern show vertical lines. The wolf carved on the bow of the same canoe shows surface patterns on its body and limbs (fig. 18). Decorative use of adzed lines, is also found on a rattle (fig. 19). In this specimen there is no technical need for the alternation in the direction of the groves, and the fields on the top of the rattle can the explained only as determined by the pleasure felt by the variation of the simple activity in novel and more complicated ways.[23] [23] See also page 41. In chipping of flint zig-zag lines are produced by the meeting of two lines on a ridge (fig. 20). [Illustration: Fig. 20. Base of flint knife, Scandinavia.] Technical experience and the acquisition of virtuosity have probably led to the general prevalence of the plane, the straight line and regular curves such as the circle and the spiral, for all of these are of rare occurrence in nature, so rare indeed, that they had hardly ever a chance to impress themselves upon the mind. Plain surfaces are represented by crystals, by the cleavage of some kinds of rock, or by the surface of water during a calm. Straight lines by the shoots and stems of plants or by the sharp edges of crystals; regular curved lines by the shells of snails, by vines, bubbles on water or by smooth pebbles, but there is no obvious motive that would induce man to imitate these particular abstract forms, except perhaps in those cases in which regularly curved shells are worn as ornaments or employed as utensils. On the other hand, the straight line develops constantly in technical work. It is a characteristic form of the stretched thong or cord and its importance cannot be ignored by the hunter who hurls a lance or flies an arrow. The technical use of the straight shoot may well have been important in its derivation. Plants like the bamboo or the reed may thus have helped man to discover the value of the straight line.