A variation in the second style used three lengths in the centerline sheathing. In still another variation a centerline piece was laid in two lengths without taper, the next outboard piece was then cut in the shape of a broad-based triangle, and the rest were laid in two lengths, with the sides parallel to the sides of the triangular strake and with their ends snied off against the centerline pieces. In a fourth style short pieces, roughly elongate-oval in shape, were overlapped on all sides and laid irregularly so that when in place they appeared "thrown in." With this style, the midship section was laid first and secured by a temporary rib, then the next toward the ends, with the butts shoved under the ends of the middle section. The next series was similarly laid so that the top member of each butt-lap faced toward the ends of the hull and was under a rib. The ends were not cut square across, but were either blunt-pointed or rounded. Five lengths of sheathing were often used, and the widths of the individual pieces of sheathing were rarely the same, so the seams were not lined up and presented an irregular appearance in the finished canoe. The sheathing was thin enough to allow it to take the curve of the bilge easily. [Illustration: Figure 29 SPLINTS ARRANGED in various ways to sheath the bottom of a canoe: 1, Micmac, Malecite; 2, Central Cree, Têtes de Boule, etc.; 3, Montagnais; 4, Algonkin, Ojibway, etc.] If the sheathing was lapped, the overlap was always slight. In some old canoes a small space was left between the edges of the sheathing, particularly in the topsides. In some northwestern bark canoes there was no sheathing; these used a batten system somewhat like that in the Eskimo kayak, except that in the bark canoes the battens were not lashed to the ribs, being held in place only by pressure. These kayak-like bark canoes had a bottom framework formed with chine members; some had a rigid bottom frame of this type, while others had bottom frames secured only by rib pressure. The purpose of the sheathing, it should be noted, was to protect the bark cover from abrasion from the inside, to prevent the ribs from bulging the bark, and to back up the bark so as to resist impacts; but in no case, even when battens were employed, as in the Northwest, did the sheathing add to the longitudinal strength of the bark canoe. The principle of the stressed rib and clamped sheathing, which is the most marked characteristic in the construction of the North American Indian bark canoe, is fundamentally different from that used in the construction of the Eskimos' skin craft.