"Flowering shrubs don't thrive in the subterranean caverns from which geysers spring," suggested Bradley.
Olson shook his head. "It beats me," he said.
"I've got it!" I exclaimed suddenly. "Look there!" And I pointed at the base of the cliff ahead of us, which the receding tide was gradually exposing to our view. They all looked, and all saw what I had seen—the top of a dark opening in the rock, through which water was pouring out into the sea. "It's the subterranean channel of an inland river," I cried. "It flows through a land covered with vegetation—and therefore a land upon which the sun shines. No subterranean caverns produce any order of plant life even remotely resembling what we have seen disgorged by this river. Beyond those cliffs lie fertile lands and fresh water—perhaps, game!"
"Yis, sir," said Olson, "behoind the cliffs! Ye spoke a true word, sir—behoind!"
Bradley laughed—a rather sorry laugh, though. "You might as well call our attention to the fact, sir," he said, "that science has indicated that there is fresh water and vegetation on Mars."
"Not at all," I rejoined. "A U-boat isn't constructed to navigate space, but it is designed to travel below the surface of the water."
"You'd be after sailin' into that blank pocket?" asked Olson.
"I would, Olson," I replied. "We haven't one chance for life in a hundred thousand if we don't find food and water upon Caprona. This water coming out of the cliff is not salt; but neither is it fit to drink, though each of us has drunk. It is fair to assume that inland the river is fed by pure streams, that there are fruits and herbs and game. Shall we lie out here and die of thirst and starvation with a land of plenty possibly only a few hundred yards away? We have the means for navigating a subterranean river. Are we too cowardly to utilize this means?"
"Be afther goin' to it," said Olson.
"I'm willing to see it through," agreed Bradley.