We were still near the bank, working our way out slowly.  Harry and I had to maintain positions equidistant from the center in order to keep the raft balanced; hence I had to push her out alone.

Considering her bulk, she answered to the oar very well.

Another five minutes and we were near the middle of the stream.  At that point there was but little current and we drifted slowly.  Harry went to the bow, while I took up a position on the stern—­if I may use such terms for such a craft—­directly behind Desiree.  We figured that we were then about a mile from the Point where the stream left the cavern.

Gradually, as the stream narrowed, the strength of the current increased.  Still it was smooth, and the raft sailed along without a tremor.  Once or twice, caught by some trick of the current, she turned half round, poking her nose ahead, but she soon righted herself.

The water began to curl up on the sides as we were carried more and more swiftly onward, with a low murmur that was music to us.  The stream became so narrow that we could see the bank on either side, though dimly, and I knew we were approaching the exit.

I called to Harry:  “Keep her off to the right as we make the turn!” and he answered:  “Aye, aye, sir!” with a wave of the hand.  This, at least, was action with a purpose.

Another minute and we saw the arch directly ahead of us, round a bend in the stream.  The strength of the current carried us toward the off bank, but we plied our oars desperately and well, and managed to keep fairly well in to the end of the curve.

We missed the wall of the tunnel—­black, grim rock that would have dashed out our brains—­by about ten feet, and were swept forward under the arch, on our way—­so we thought—­to the land of sunshine.

Chapter XX.

An Inca spear.

Here I might most appropriately insert a paragraph on the vanity of human wishes and endeavor.  But events, they say, speak for themselves; and still, for my own part, I prefer the philosopher to the historian.  Mental digestion is a wearisome task; you are welcome to it.

To the story.  As I have said, we missed the wall of the tunnel by a scant ten feet, and we kept on missing it.  Once under the arch, our raft developed a most stubborn inclination to bump up against the rocky banks instead of staying properly in the middle of the current, as it should.

First to one side, then to the other, it swung, while Harry and I kept it off with our oars, often missing a collision by inches.  But at least the banks were smooth and level, and as long as the stream itself remained clear of obstruction there was but little real danger.

The current was not nearly so swift as I had expected it would be.  In the semidarkness it was difficult to calculate our rate of speed, but I judged that we were moving at about six or seven miles an hour.