Traditions of long voyages by the ancient Irish in the skin-covered curragh make it apparent that such voyages were relatively common, and the design and construction of existing models of the curragh and umiak indicate that these voyages could have been made with reasonable safety. Compared to the dugout canoe, the skin boat was far lighter and roomier in proportion to length and so could carry a far greater load and still retain enough freeboard to be safe. The size of the early skin boats cannot be established with certainty; the modern Irish curragh is probably debased in this respect, but early explorers of Greenland reported umiaks nearly 60 feet in length and there is no structural reason why the curragh could not have been as large or even larger. Compared with the curragh, the umiak is lighter, stronger, and more resistant to shock. The curragh was built with closely spaced bent frames and longitudinal stringers to support the skin cover, whereas the umiak has very widely spaced frames and few longitudinals, giving the skin cover little support. The difference in construction is undoubtedly a result of the type of covering used, for the curragh was covered with cattle hides, which were less strong than the seal or walrus skins used by the Eskimo. The strong and elastic skin cover of the umiak and the lack of a rigid structural support gives this boat an advantage in withstanding the shocks of beaching or of working in floating ice; and because of its relatively light framework and the method of securing the structural members, its frame is far more flexible than that of the curragh, adding to this ability. The skin cover of the curragh was made watertight by rubbing the hides with animal fat, and the sewn seams were payed with tallow. The Eskimo soak the skin cover of the umiak with animal oil and pay the seams with blubber or animal fat. Both treatments produced a cover initially watertight but requiring drying and reoiling to remain so. Under most climatic conditions in the North Atlantic or Pacific the oiled skins remain watertight from four days to a week. This period can be lengthened by various methods; skin boats travelling in company can be dried out in turn by unloading one and placing it aboard a companion craft. There is evidence of other methods of treating the skin covering; waterproofing it with melted tallow, for example, or with a vegetable gum or a resin such as pitch, would enable it to remain watertight for a much longer time, though such treatments would make the covering less elastic. Pitch was also used at one time in curragh building, and it would be unwise to assume that the oil treatment used by the Eskimo was their only method of producing watertight skin covers in the period before they were first observed by Europeans. [Illustration: Figure 158 WESTERN ALASKAN UMIAK with eight women paddling, Cape Prince of Wales, Alaska, 1936. (_Photo by Henry B. Collins._)] [Illustration: Figure 159