rints
made by the captive, lightly pressed. These tracks followed the
curving bar, along the water's edge. They reached to the foot of the
cliff, close to where was the outer edge of the cataract. There they
ceased.

The marshal, already familiar with the mystery, and baffled by it,
searched again perfunctorily. Uncle Dick hunted hither and yon with
feverish activity, at first confidently, then doubtfully, finally in
despair. He, in his turn, could find no further clue. He gave over his
efforts eventually, and stood silent beside the marshal, staring
bewilderedly. About the amphitheatre formed by the pool, pines grew in
a half-circle, save where the narrow channel of the stream descended.
But between the barricade of the trees and the basin of water lay the
smooth stretch of sand, slightly moist from out-flung spray of the
falls. Upon that level surface, the tracks showed forth--undeniable,
inexplicable. They marched without deviation straight to the base of
the great cliff. There, within a little space, they grew confused, as
from much trampling. But they did not return; they did not go
elsewhere. There was a clear distance of a rod over the sand to the
rocky ground where the trees grew. On the other side lay the deeps of
the pool. Before them reared the impassible wall of the precipice. And
there the tracks ended.

Uncle Dick knew the place well, and on that account the mystery was
the greater. He could find no possible explanation, however wildly
improbable, of that disappearance. The broad sheet of the falls fell
close to the cliff's face. The rock was unworn by the torrent, without
recess or cavern. And that precipice, twice the pool's width, mounted
sheer a hundred feet, the height of the cascade. The front was
unbroken save by tiny rifts and narrow ledges, where dwarfed ground
pines clung precariously. With a muttered curse, the old man turned
from his vain contemplation of the cliff, and let his troubled eyes
rest on the pool. Suddenly, he started. He remained motionless for a
moment, then, with nervous haste threw off his shirt, and trousers.
Marshal Stone, chancing to look that way, was astonished to see his
companion naked, poised at the water's edge. He had time to note with
admiration the splendid figure, still supple and strongly muscled
despite the four-score years. Then Uncle Dick leaped, and dived. It
was long seconds before he reappeared, only to dive again. He paid no
attention to the marshal's rem