“Crude rafts and hollowed-out cottonwoods were not suitable for commercial loads. The fur traders first attempted a modification of the circular Indian bullboat. This was an ingenious contrivance, resembling an enormous oval basket yp to twenty-five feet in length. The framework was composed of long and pliable poles from green aspen or willow. This was covered with dressed buffalo hides sewn together and then soaked. The shrinkage produced a tight covering, the seams of which were made water-tight by a mixture of buffalo fat and ashes. This resulted in a craft of extreme buoyancy which could transport up to three tons without displacing more than ten inches of water. The bullboat could be quickly and easily manufactured, but it would as easily be wrecked by snags and hidden bars in shallow water, and in deeper water would readily capsize.”