On the way up, their caravan had crossed a stream by means of a bridge constructed on the cantilever principle, as is common in that country. It occurred to Bob that there was a possibility of constructing a walk along the face of the cliff on the same principle. "It will be a series of bridges made of overlapping planks," he said to Lawrence when explaining his idea. "There’s plenty of timber in the shed." "Which Uncle won’t allow to be used." "I’ll talk him over." "But I don’t see how you’re going to manage it. There are no supports." "They are easily managed. All we’ve got to do to is drive beams into the rock, say twenty feet apart." "Exactly; but how are you going to make holes in the rock? There’s nothing to stand on, and we can’t rig up scaffolding from the bottom of the river." "I think we can do it all the same. What we have to do is to go to the extreme edge of the ledge of the silver mine, bore a couple of holes in the rock level with our heads, and drive in poles strong enough to support a swinging platform. You’ve seen house painters use them on house fronts at home. We can extend that with some planks, and so reach a position where similar holes can be bored a little farther away, and so on until we reach the farther ledge. A couple of stout miners on the platform can easily bore the holes, level with it, that we require for the larger beams, and when they are placed it will be a comparatively simple matter to lay planks upon them, and carry our cantilever walk the whole way. We can use the upper poles too: connect them by a rope, which we can cling to as we push the parts of the machine along on trolleys." "It will take a very long time," said Lawrence dubiously. "Not so long as you think if we can only persuade the old man to let us have a couple of men to work at it continuously. I’ll tackle him to-night after supper when he’s comfortably settled with a cigar." Mr. Appleton happened to be in a very amiable mood when Bob broached the subject, and though he uttered doleful warnings and foretold broken limbs, and declared that he washed his hands of all responsibility, he told the boys that they might do as they pleased. Next day they invited volunteers from among the Kalmuck miners, and were somewhat surprised when Nurla Bai was the first to offer his services, explaining that he was an expert in carpentry. Taking this as a sign of grace, Bob engaged the man, and told him to choose his own assistant. Nurla at once suggested a dwarfish man named Tchigin, a thick-set, muscular fellow with a huge head covered with jet-black hair. Mr. Appleton called him Black Jack. They began work, and Bob was well pleased with their industry and skill. Before night there was a row of half-a-dozen of the smaller poles in position, and all was ready for the drilling of the larger hole for the first of the stout beams that were to support the wooden path.