One necessary precaution could be taken in advance. It was to discover by experiment the length of rope needed. Bob guessed that the ledge on which he stood, at the narrow end of the cleft farthest from the ravine, must always have formed the springing-ground; its position therefore governed the length. Having explained to his two companions what he had in mind, he cut their expostulations short by borrowing some of their upper garments, which he made into a soft bundle. He weighted this with some heavy stones, tied it to the rope, and then, as the moon threw a dim light on the opposite side of the ravine, he placed the bundle in Ah-Sam’s hands and made his way to the neighbourhood of the girder. Arriving there, he lifted his hand as a signal to the Chinaman to loose his hold on the bundle, and anxiously watched its course. It swept through the cleft, across the ravine, came to rest apparently within a yard of the platform, then swung back, making a giddy oscillation and narrowly escaping the wall of the cleft, until as it approached the ledge Ah-Sam caught it by means of a noose in a shorter rope. Its unsteady return journey gave Bob some alarm, but he surmised that with the greater weight of a man the rope would probably have risen higher and taken a more direct backward swing. The experiment was sufficiently satisfactory, and then Bob explained to his amazed listeners what he proposed to do. He would himself risk the attempt. If he got safely across he would fix the rope to the staple and make a preliminary investigation of the pathway leading upwards from the platform. Should he require assistance he would return and loosen the rope, which would then swing back to a position perpendicularly under the girder. Ah-Sam meanwhile was to crawl to the extreme end of the ledge just below the bar; he was to obtain a hold of the rope as it swung loose, return to the innermost end of the cleft, and swing across the ravine as Bob had done. On the other hand, if Bob found that nothing could be done from the platform, or if he were detected, Ah-Sam was to cover his retreat with the revolver. "What Sing-Cheng do allo tim’?" asked Ah-Sam when he had grasped his own instructions. "He will remain behind. Tell him so." When the chief understood this he was greatly indignant, and began to protest in loud tones. Bob checked him peremptorily. He felt that if he gained admittance to the fort precious time would be wasted if he had to give orders to Sing-Cheng through Ah-Sam, while if two men were unable to effect their purpose it was unlikely that three would succeed. He did not consider it necessary to argue with the chief, but pacified him by saying that, if Ah-Sam crossed over, he was to take the Chinaman’s place at the end of the cleft and watch carefully lest it proved necessary to cover the retreat of the two from the other side.