[4] See bibliography. The skin cover of the north Alaskan whaling umiak is made of bearded seal or of walrus hide, which has to be split, because of its weight. Occasionally polar-bear skins are used. Lashings of the frame are of whalebone, sinew, and hide. The skins are treated with seal oil and caribou fat, and when the whaling umiak is taken ashore it is usually stored on a stage to keep dogs from destroying the skin cover. In travelling, however, it is sometimes propped upside down on one edge and used as a shelter. In winter the skin is removed and stored; when it is necessary to be replaced on the frame, the skin cover is soaked in sea water for three to five days, after which it is laced on in the usual manner, dried, and then thoroughly oiled. Low, rather wide sledges are sometimes built to carry the umiak overland, or on the ice, but often the regular sledge is used. The boats cannot be sledged against a strong gale because of their windage. The north Alaskan umiak is usually propelled by paddles, like the Chukchi umiak. These paddles range in length from about 50 to 76 inches, and as a rule have a rather long narrow blade, though a short and wide blade is occasionally found, particularly at Kotzebue Sound and Point Hope. Oars for the Alaskan umiaks range in length from 6 feet 3 inches to 8 feet 6 inches, and also have rather long narrow blades, 3 to 4 inches wide. The three examples of Alaskan umiaks serve to show the features that are most common in the area. However, models in the U.S. National Museum suggest that there was a greater variety of form and appearance in the past. One model shows the gunwale ends lengthened by pieces shaped very much like the projecting gunwales of the Malay prah. Some show extreme rake at the bow like that of the Koryak umiak but without the rounded gunwale ends. It is impossible to estimate how far the western Alaska umiak model has been affected by the early Russian traders in this area, but it is quite certain that the use of oars can be traced to this influence. The full-sized umiaks, and models and photographs, from the Bering Strait area give no real clues to the possible parentage or direction of spread of the Alaskan umiak types. Occasional details in fittings or construction, such as the gunwale extensions mentioned, seem to duplicate details in primitive Asiatic craft, but the evidence is too scanty to allow a hypothesis based on design and construction alone. [Illustration: Figure 173 EAST GREENLAND UMIAK, drawn from measurements taken off by a U.S. Army officer in 1945.] No models or photographs have been found of the extinct types of umiaks once used in the northern part of Hudson Bay and the sketches of early explorers are too crude to allow useful discussion. From such slight evidence it is impossible to say whether the umiaks in this area were of the western or eastern type.