“Take a chance,” he advised.  “Why not?  As well that as anything.”

We slipped through the entrance.

The current was extremely sluggish, and we barely seemed to move.  Still we went forward.

“If we only had a little speed we could stand it,” Harry grumbled.

Which shows that a man does not always appreciate a blessing.  It was not long before we were offering up thanks that our speed had been so slight.

To be exact, about an hour, as well as I could measure time, which passed slowly; for not only were the minutes tedious, but the foulness of the air made them also extremely uncomfortable.  Desiree was again lying down, half-unconscious but not asleep, for now and then she spoke drowsily.  Harry complained of a dizziness in the head, and my own seemed ready to burst through my temples.  The soroche of the mountains was agreeable compared to that.

Suddenly the swiftness of the current increased appreciably on the instant; there was a swift jerk as we were carried forward.  I rose to my knees—­the tunnel was too low to permit of standing—­and gazed intently ahead.  I could see nothing save that the stream had narrowed to half its former width, and was still becoming narrower.

We went faster and faster, and the stream narrowed until the bank was but a few feet away on either side.

“Watch the stern!” I called to Harry.  “Keep her off with your spear!”

Then a wall loomed up directly ahead.  I thought it meant another bend in the stream, and I strained my eyes intently in the effort to discover its direction, but I could see nothing save the black wall.  We approached closer; I shouted to Harry and Desiree to brace themselves for a shock, praying that the raft would meet the rock squarely and not on a corner.

I had barely had time to set myself and grasp the straps behind when we struck with terrific force.  The raft rebounded several feet, trembling and shaking violently.  The water was rushing past us with noisy impetuosity.

There was a cry from Desiree, and from Harry, “All right!” I crawled to the bow.  Along the top the hide covering had been split open for several feet, but the water did not quite reach the opening.

And we had reached the end of our ambitious journey.  For that black wall marked the finish of the tunnel; the stream entered it through a narrow hole, which accounted for the sudden, swift rush of the current.  Above the upper rim of the hole the surface of the water whirled about in a widening circle; to this had we been led by the stream that was to have carried us to the land of sunshine.

When I told Desiree she stared at me in silence!  I had not realized before the strength of her hope.  Speechless with disappointment, she merely sat and stared straight ahead at the black, unyielding rock.  Harry knelt beside her with his arm across her shoulders.

I roused him with a jerk of the arm.