"But--but," faltered Dick. "It may be too late to save him when this side passage fills up." "What I was going to propose," went on Bud, "is that we see if we can't follow along this newly-discovered side passage, as we have been following the main bed of the underground river." He paused to let his companions visualize this suggestion. "Do you think that would be safe?" asked Old Billee. "I mean," he added quickly, "will that be th' safest way t' try an' save Nort? I won't back down on anything--I guess you know that--but I was just wondering if there was some other way." "There might be," said Bud. "We could go along on the left side of the stream, and see if there is a crossing place farther on. We saw some narrow places when we were here before, but it's a question how much water they'd have in them now." "Oh, but can't we do something?" cried Dick, now almost sobbing, though he was making a brave effort to conquer himself. "Oh, Nort! Nort! Where are you?" he cried frenziedly. But again only the echoes answered. "Come on!" cried Old Billee suddenly. "We'll try this way. We've got t' do something!" "Leave our packs here," suggested Yellin' Kid, and again his voice was low, as if in deference to Dick's feelings. "We can put 'em up on that ledge," he added, indicating a small one on their side of the underground stream. "The water doesn't appear to have been up there in years. If we leave our things here we'll be better able to help Nort--if we find him," he added in a voice so low that only Old Billee heard. "Take our lanterns," suggested Snake Purdee. "And ropes," went on Bud. "We may need 'em!" Accordingly the food and other supplies, which the searchers after the secret of the underground water course had brought with them, were put up on the ledge, and then they started down the black passage through which the stream appeared to have branched, carrying Nort with it. There was room but for one to walk at a time on this "bank," as it might be called, of the hidden stream, and they had to proceed in single file. "I'd like to see a map of this place, so we'd know where we were going," spoke Old Billee, as he swung his lantern from side to side in an endeavor to disclose the hidden secrets of the place. "I have an idea that the underground stream is shaped like the letter T," spoke Bud. "The top, or cross stem, is the part that extends from the river to our reservoir. We are now walking along the upright piece." "But if the main part of the T is also a stream, and the water is running down that, as it is, instead of along the main stem, it becomes for the time being a letter L, doesn't it?" asked Snake. "Yes," assented Bud. "And as long as the water turns at right angles, as it does at the place where Nort fell in, and as long as the water runs along this same side passage, we don't get any at Flume Valley. The letter T is in our favor, and L is against us."