We were already rather close in; but I ordered the _U_-33’s prow turned inshore and we crept slowly along, constantly dipping up the water and tasting it to assure ourselves that we didn’t get outside the fresh-water current. There was a very light off-shore wind and scarcely any breakers, so that the approach to the shore was continued without finding bottom; yet though we were already quite close, we saw no indication of any indention in the coast from which even a tiny brooklet might issue, and certainly no mouth of a large river such as this must necessarily be to freshen the ocean even two hundred yards from shore. The tide was running out, and this, together with the strong flow of the freshwater current, would have prevented our going against the cliffs even had we not been under power; as it was we had to buck the combined forces in order to hold our position at all. We came up to within twenty-five feet of the sheer wall, which loomed high above us. There was no break in its forbidding face. As we watched the face of the waters and searched the cliff’s high face, Olson suggested that the fresh water might come from a submarine geyser. This, he said, would account for its heat; but even as he spoke a bush, covered thickly with leaves and flowers, bubbled to the surface and floated off astern. “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.