By and by they came to a stream of some size, flowing north and south. Bob guessed that this must be the stream that ran through the ravine; it gave him hope that he was on the right track. He looked along the surface of the water for the roughness that would indicate a ford. At that spot they crossed, tying themselves together with the straps of their baskets to prevent themselves from being swept away by the rapid current. Having crossed, they pushed on without a halt, up the left bank, and arrived somewhat late in the afternoon at an elevated spot, where they came suddenly in sight of the fort, a mile or more below them. Sing-Cheng’s eyes gleamed as he saw the stronghold of his enemy. He stretched his right arm towards the place and began to speak excitedly. Bob pulled him behind a rock. It was not unlikely that Chang-Wo among his many precautions had set a sentry to watch this part of the surroundings of the fort, even though the ravine rendered it unassailable from this direction. Keeping well in cover, Bob himself took a long look at the stronghold that was now more important to him than anything else in the world. What he saw was an irregular fortress, probably a hundred yards in diameter, built on the edge of the ravine, which appeared a black strip in the distance. There were five flanking towers, two resting on the ravine, the other three disposed somewhat irregularly on the outer wall; this was evidently of considerable height. In the whole enceinte there was, so far as Bob could see, only one gateway, on the farther side. Allowing for his distance from it, and for the slight slope of the intervening country, he estimated that the ravine was wide; and from the general lie of the land, and his own experiences of the lower course of the river, he knew that it must be of great depth. On the near side of the ravine, almost exactly opposite the fort, he noticed that the edge was broken by a narrow cleft running at right angles to it. Beyond the fort the country was bare and rolling to the north, but to the west and south was much broken up by knolls and plantations of fir. The gray stone walls stood out in clear relief against the background. Within the enclosure scores of figures were moving about between the low buildings; it was like an ant-hill for activity; and on the rising ground beyond the farther wall Bob descried more than one ragged encampment, confirming what had been told in the inn about the careful guard maintained on the only practicable line of approach.