Clay chuckled to himself, and went into the cabin after Alex.
"Come on, Redhead!" he cried catching the boy by the arm. "We are now going ashore to dig up the lost channel."
"That's a nice pleasant little job, too!" Alex declared.
"Well, come on," Clay insisted. "We'll go over and make a start, anyway. We may be able to find out if the outlaws are really here."
Explaining to Captain Joe and the others that they were going only a short distance from the shore, the boys launched the canoe and were soon on the sloping shore of the peninsula. Once across they hid their canoe in a thicket which overhung the stream and disappeared in the interior.
"Now, look here," Clay said as he stopped and sat deliberately down in the shade of a great tree, "I've got an idea."
Alex stared hard in pretended wonder and amazement.
"Brain cell opened and gave it to me," Clay answered.
"Captain Joe wants to know where the water comes from to make the west river so large at its mouth," Clay went on. "I started in to tell him that there might be a subterranean stream somewhere hereabouts, but I thought he would laugh at me and so kept my mouth shut."
Alex sprang to his feet and swung round and round on his heels, chuckling and shaking hands with himself.
"That's the idea!" he cried. "That's just the idea! There is a subterranean stream here somewhere! Look at the way the rocks are piled up, and look at the long slope from the top of the ridges to the level of the river. There are catch basins here somewhere, and water pouring into the river that no one knows anything about."
"Now go a little farther," Clay suggested. "Figure that at some time, say two or three hundred years ago, this subterranean channel lay open to the sun. Now what do you make of it?"
"Holy smoke!" almost shouted Alex. "I make a lost channel!"
"There you are!" Clay began, "and all we've got to do is to just look around and find it. We've got plenty of time."
"That will be some cheerful job, too," Alex commented. "We've only got about forty thousand square miles of territory to look over."
"I think," Clay said, "that we have the idea, and that is the main thing. The rest is only a matter of detail."
As the boys sat under the tree, Alex having dropped down to the turf again, a rustling of bushes was heard to the east and they turned in that direction, scanning the thicket closely. Then Alex seized Clay by the arm and pointed away through the underbrush.