Frank remembered that this, or something like it, was the ancient practice, and that it was only by slow degrees that man had discovered he could still make the wind propel his vessel to its destination when it blew from ahead. Greek and Roman triremes, Alexandrian wheat ships, and Viking galleys, had made wonderful voyages, and they all carried sail, but they set it only when the wind was fair. When it drew ahead they stowed their canvas and thrashed the lean hull through the seas with their long oars. Now, after perfecting his vessel's under-water body, inventing the center board, and learning how to make flat-setting sails, man was going back to the old-time plan, only that instead of relying upon the muscle of close-packed rowers he used improved propellers, tri-compound reciprocators and turbines. One of the Siwash shook out the two spritsails which sat on a pole stretching up to the peak from the foot of the mast, and when he had led the sheets aft his companion knelt astern with a paddle held over the gunwale. Slanting gently down to the faint breeze, the craft slid away through the smooth, green water with a long ripple running back behind her. The log houses dropped astern and were lost among the trees, a valley filled with somber forest, and a rampart of tall hillside, slipped by, and as they crept on from point to point the strip of still water stretched away before them between somber ranks of climbing trees. Frank had no idea how far they had gone when the light began to fail, though he fancied that the shallow craft, now slipping forward so smoothly, was sailing a good deal faster than she seemed to be. At length one of the Siwash loosened the sheets and stowed the sails, while his companion turned the bows toward the beach. She slid in and grounded gently on a bank of shingle in a little cove, where a gigantic forest crept down to the water. They got out and ran her up, filled their kettle at a tinkling creek, hewed resinous chips from a fallen fir, and built a fire. Then they cut armfuls of thin spruce branches with which to make their beds, and presently sat down to an ample supper.