When he passed it at last his task was done, for the cave was a stone's toss away. It was not even then to be seen, and its presence in the cliff would scarcely have been suspected. But Grenville knew the luxuriant plant that grew across a portion of its entrance. When he presently moored his raft to a rock fairly under the shadow of the weed, the cave was just above him.
Under his feet the ledge was rough and sloping. It was pitted so completely as to form a rude natural stairway to the opening under the overhanging shelf. This mouth to the cavern was hardly six feet wide and not more than four in height. Its access was comparatively easy.
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.