The situation was a simple one, yet one that called for nerve and unbounded courage. Immediately opposite the cleft, on the other side of the ravine, was the small rocky platform, with a staple in the wall above. The width of the ravine, as Bob estimated, was some eighty feet, but it was impossible to make any more accurate calculation; it might be more than eighty, it might be less; and a few feet one way or the other would make all the difference in the plan he had conceived. He had come to the conclusion that the iron girder which had so much piqued his curiosity had an intimate connection with the platform and staple. It had been there in the old chief’s time; nobody knew when or why it had been placed in position, but Bob felt convinced that girder and platform had been intended to serve as a means of ingress to or egress from the fort if it should chance to be invested. A besieging force, relying on the apparent impossibility of scaling the side of the ravine, would be unlikely to maintain a guard there. But Bob’s idea was that, suspended from a rope fastened to the girder, an active man could swing across the chasm, and, if the length of the rope were properly adjusted, could land gently on the platform, make good his footing by grasping the staple, and thereby prevent himself from falling backward with the return swing of the rope. If the rope were too long, he would of course run the risk of being dashed against the wall of the ravine beneath the platform. If it were too short, he would fail to reach the staple and swing back into the cleft; and as the return swing would obviously not carry him to his starting-point, he would again swing across the ravine, and so the pendulous movement would continue until he came to rest perpendicularly beneath the girder. He would then either have to climb the eighty feet of rope until he reached the iron bar, or drop the sheer two hundred feet to the bottom of the cleft. There was a further danger. On the return swing the man might, owing to oscillation in the rope, fail to enter the cleft, and be carried against its jagged edge, probably with sufficient force to stun, disable, or even kill him. Clearly the attempt would be full of danger; but it was this hazardous feat that Bob had resolved to attempt.