The frame of the bullboat was constructed by laying stout willow poles, three or four inches in diameter, lengthwise of the boat, and across these similar poles, the two layers being firmly lashed together with rawhide. The side frames were made of willow twigs about an inch and a half in diameter at the larger end and six to seven feet long. The smaller ends were lashed to the cross-poles, and about two feet of the larger ends were then bent up to a vertical position. Along the tops of the vertical portions and on the inside was lashed a stout pole like those forming the bottom of the framework. To this gunwale were lashed cross-poles, at intervals of four or five feet, to keep the sides from spreading. No nails or pins were used for fastenings, but rawhide lashings only. The frame so constructed was exceedingly strong, and its flexible quality, by which it withstood the continuous wrenching to which it was subjected, was an important element of strength. [Sidenote: METHOD OF CONSTRUCTION.] The framework, being completed, was then covered with a continuous sheet of rawhide formed by sewing together square pieces as large as could be cut from a single buffalo hide. Only the skins of buffalo bulls were used for this purpose (whence the name of the boat), for they were the strongest and best able to resist abrasion from rubbing on the bottom of the river. The pieces were sewed together with buffalo sinew. Before this work was done the hides were carefully dressed by the Indians so as to be free of hair and perfectly flexible. When the covering was all sewed together it was thoroughly soaked and then placed over the framework and the sides and ends made fast to the gunwale of the boat. The hides would then dry and shrink until they were drawn as tight as a drumhead. The final operation in the work was to pitch the seams. The material used was a mixture of buffalo tallow and ashes, and it was carefully rubbed into all seams or cracks until the whole covering was water-tight. [Sidenote: NAVIGATION BY BULLBOAT.] The boat so built was very light, and could be easily turned over by two men. When in the water and ready for its cargo, a layer of loose poles was laid lengthwise on the bottom so as to keep the cargo five or six inches from the bottom and protect it from any water that might leak in. The cargo nearly always consisted of furs, securely packed in bales about thirty inches long, fifteen inches wide, and eighteen inches deep. They were placed one bale deep over the bottom of the boat, leaving space in bow and stern for the pole men. The bales were always laid flatwise, so that if the water should reach them it would injure only the bottom skins and not all, as it would if they were set edgewise. The cargo rarely exceeded six thousand pounds.