Scrambling up this mass of earth and rocks, we went on, keeping a sharp lookout for some sign of a pathway up the cliff on our right, but still seeing nothing of the sort, when presently we reached the upper face of the dam, and there for a moment we stopped.
Beneath us lay a stretch of the ravine, forming a basin about two hundred yards long, in the bottom of which were three or four pools of clear water. At the upper end of this basin was a perpendicular cliff, barring all further advance in that direction, over which, in some seasons of the year, the water evidently poured—sometimes in considerable volume apparently, judging from the manner in which the sides of the basin had been undermined. The sides themselves continued to be just as unscalable as ever; in spite of Dick's assurance that we should find a way up, it was apparent at a glance that there was neither crack nor crevice by which one could ascend.
"Well!" cried my partner, in a tone of desperation. "This does beat me! I felt certain that the trail would lead us to some pathway up the cliff; but, as it does not, what does it come down here for at all?"
"There is only one reason that I can think of," I replied, "and that is that they must have come down here for water—there is probably none to be found up on top of the 'island.'"
"That must be it, Frank. Yes, I expect you've struck it. And in that case the pathway we have been hunting for must be down stream from the site of the old bridge after all."
"Yes. So we may as well go back to-morrow morning, I suppose, and start downward. It is rather late to go back now—and besides, there is no water up there: we had better camp here for to-night, at any rate."
"That's true. Well, as we have some hours of daylight yet—if you can call this daylight down here in this narrow crack—let us climb down the face of the dam and examine the basin before we give up and go back, so as to make quite sure that there is no way up the side."
Accordingly, having clambered down, we walked up the middle of the basin, our eyes carefully scanning the wall on our right, when, having traversed about three-quarters of its length, we suddenly heard again that humming noise which we had taken for a wind-storm among the pines. With one accord we both stopped dead and listened. The noise was decidedly louder than it had been before, and moreover it appeared to be increasing in volume every second.
"Frank!" exclaimed my companion. "I don't like the sound of it! It seems to me suspiciously like water! Let us get out of here! This is no place to be caught by a flood!"
We turned to run, but before we had gone five steps we heard a roar behind us, and casting a glance backward, we saw to our horror an immense wall of water, ten feet high, leap from the ledge at the end of the basin and fall to the bottom with a prodigious splash.