The bed of the stream has been scooped out of the solid rock. Here and there banks of sand have been deposited, and accumulations of loose stone disguise the real nature of the channel. Great boulders have been rolled down the alleyway and left where they chanced to stick; the stream must get around them or under them as best it can. But there are other places where everything has been swept clean; nothing remains but the primitive strata, and the flowing water merrily tickles the bare ribs of mother earth.
Whirling stones, in the spring floods, have cut well-holes in the rock, as round and even as if they had been made with a drill, and sometimes you can see the very stone that sunk the well lying at the bottom. There are long, straight, sloping troughs through which the water runs like a mill-race. There are huge basins into which the water rumbles over a ledge, as if some one were pouring it very steadily out of a pitcher, and from which it glides away without a ripple, flowing over a smooth pavement of rock which shelves down from the shallow foot to the deep head of the pool.
The boy wonders how far he dare wade out along that slippery floor.