The tunnel extended all the way through Snake Mountain, curving this way and that, as a brook curves its way through a meadow. In fact the tunnel had been made, centuries ago, by a stream forcing its way through the soft parts of the mountain, and it was this old, hidden, underground stream-way of which Mr. Merkel had taken advantage to bring water to Flume Valley. The stream flowed along the bottom of the tunnel course, leaving room on either side for persons to walk, as they might walk along the banks of a stream in the open. The underground river was not more than four feet wide, and about the same in average depth, but in places it flowed with a very powerful current. "Whew! It's black as tar here!" exclaimed Dick, as they walked in past the pipe, and found themselves in the tunnel proper. "As bad as the Hole of Calcutta," added Nort, who had read that grim story of the Sepoy rebellion in India. "Do you want to back out?" asked Bud, swinging his lantern so that it cast flickering shadows on the place where water had flowed, but where there was none now. "Back out!" cried Nort. "I should say not! Lead on, Macduff!" And they started off in the blackness of the tunnel, with only the faint gleams of the lanterns to illuminate their way. What would they find? CHAPTER XI THE RUSH OF WATERS Echoes of the footsteps of the boy ranchers sounded and resounded as they tramped along the now dry water-course of what had, only a day before, been a life-giving stream of water. The rocky and roughly-vaulted roof overhead gave back the noises like the soundbox of a phonograph, and the lads had to speak loudly, in places, to make their voices carry above the echoes. These places were spots where the vaulted roof of the tunnel was higher than usual. They had walked on, the semi-circular spot of light at the entrance near the black pipe growing more and more faint, until it was not at all visible. "There she goes!" exclaimed Dick, looking back. "What?" asked his brother. "The last gleam of daylight," was the answer. "If anything happens to our lanterns, so that they go out, and we get mixed up in some branch passages--good night! That's all I have to say!" and Dick was very emphatic in this. "By Zip Foster!" exclaimed Bud, using that expression for the first time in several days. "You're a cheerful chap to have along on a picnic like this, Dick! Not!" "Well, might as well prepare for the worst and hope for the best," laughed Dick, while Nort inquired: "Why don't you tell us more about Zip Foster?" "Oh--you--say, did you hear anything then?" asked Bud, and his voice had in it such a note of anxiety that his companions did not, at the time, imagine he might have been putting them off from a much-wanted and often-delayed explanation of this mysterious Zip Foster personage. "Hear what!" asked Dick.