The surface was perfectly level, and we set off at a brisk pace, hand in hand, directly away from the lake. But when, about a hundred yards off, we suddenly bumped our heads against a solid wall of rock, we decided to proceed with more caution.
The darkness was intensified, if anything. We turned to the right and groped along the wall, which was smooth as glass and higher than my best reach. It seemed to the touch to be slightly convex, but that may have been delusion.
We had proceeded in this manner some hundred yards or more, advancing cautiously, when we came to a break in the wall. A few feet farther the wall began again.
"It's a tunnel," said Harry.
I nodded, forgetting he could not see me. "Shall we take it?"
"Anything on a chance," he answered, and we entered the passage.
It was quite narrow—so narrow that we were forced to advance very slowly, feeling our way to avoid colliding with the walls. The ground was strewn with fragments of rock, and a hasty step meant an almost certain fall and a bruised shin. It was tedious work and incredibly fatiguing.
We had not rested a sufficient length of time to allow our bodies to recuperate from the struggle with the torrent; also, we began to feel the want of food. Harry was the first to falter, but I spurred him on. Then he stumbled and fell and lay still.
"Are you hurt?" I asked anxiously, bending over him.
"No," was the answer. "But I'm tired—tired to death—and I want to sleep."