Grenville, with his torch in hand, was presently gazing within. Obliged to stoop, and beholding nothing but absolute darkness ahead of his light, he stumbled against a lumpy vein of rock—and nearly met with disaster. He barely halted at the edge of a pool of ebon water.

After all his effort to gain the cave, it appeared to be filled with this inklike accumulation. The pool was absolutely still. Not a ripple disturbed its shining surface. How deep it was and how far it extended from the ledge that held it from flowing into the sea, could not be gauged by Grenville's torch, as he held it aloft to stare at the wall of velvet gloom.

He sounded a note that rolled about and reverberated weirdly. But he could not determine from the echoes how far the waves had traveled.

Casting his dull-red illumination to the left, and lower down, he proceeded a little along the ledge, till it merged in an upright wall. There was nothing at all to be seen in this direction save water and rock, that faded away into Stygian darkness beyond.

He retraced his steps and explored the ledge on the right. This led him considerably further than the first had done before it was similarly ended. He was then aware the cavern was of no inconsiderable dimensions, at least with regard to its width. He raised his eyes towards the ceiling, where nothing was to be seen.

At length he bethought him of another test—that of throwing lumps of rock against the walls. There were fragments in plenty scattered loosely at his feet. The first one he threw went straight out ahead—and presently thumped on something solid. He reckoned the distance some sixty feet away, but admitted it might have been eighty.

Every missile he cast right, left, or at an angle promptly reported a wall; and some plumped back into water. The cave was not gigantic, but all its floor was apparently flooded. His hand, which he thrust in the water where he stood, groped blindly and found no bottom. He rolled up his sleeve and tried again, without more definite results. The water, however, was warm.

"Good place for a swim, in any case," he told himself, aloud; and, planting his torch with a sudden determination that he would not retreat with information so utterly meager, he stripped off his clothing at once. He let himself into the ebon depths, with his torch held well above the water. He had rather expected to be able to wade, but he sank to his neck without sounding to the bottom.

Swimming almost perpendicularly, employing one hand only, he presently lost all sight of the walls and was out in an unknown pool of blackness. Save for a slight sensation of its weirdness, the experience was decidedly pleasant. He tasted the water as he swam and found that it was fresh. He turned to look out at the opening, but could barely see light through the weeds.

Some twenty or thirty feet from the ledge, his feet encountered a ridge. It was stone, and across it he waded to a greater depth beyond. Yet once again he was soon enabled to stand erect and walk along the bottom. The broken, uneven surface that he felt with his feet made his progress slow and careful.