The sound of my own voice, coming immediately after that terrible thrice-repeated cry, seemed somehow comforting and reassuring, and I now awaited a reply to my hail with a feeling in which there was more of curiosity than horror.  But no reply came; and I once more lifted up my voice in tones of appeal and encouragement.  Then, since I failed to evoke any response, I put the boat's helm down, and tacked, the conviction being strong within me that I could hit off, to an inch, the exact spot from which those dreadful sounds had come.  So firmly convinced, indeed, was I of my ability to do this that when the boat came round I left the staysail sheet fast to windward, eased off the fore sheet, and stood by, leaning over the lee gunwale, in readiness to seize and haul inboard the drowning wretch who, I was fully persuaded, must be now almost under the boat's bilge.  But, although the starlight was sufficiently brilliant to have betrayed, at a distance of seven or eight yards, the presence of such an object as a man clinging to a piece of floating wreckage, I could see nothing, no, not even so much as a scrap of floating weed.  That I was bitterly disappointed--and also somewhat frightened--I freely admit; for I had somehow succeeded in convincing myself that those terrifying sounds had issued from the throat of a human being so close at hand that I could not possibly fail to find him; yet I had _not_ found him; had failed, indeed, to find the slightest suggestion of his presence; and if those sounds had not a human origin, _whence came they_?  It was the mystery of the thing, as well as the weird, unearthly character of the cries, that sent a thrill of horror through the marrow, and made me almost madly anxious to find an explanation.  I worked the boat to and fro athwart those few square yards of ocean for a full hour or more, and shouted myself hoarse, until I at length most unwillingly abandoned the search, and squared away to place as many miles as possible between myself and that unhallowed spot ere I attempted to sleep.