"He's laughing at us," growled Mr Staples. "Oh, if we could send a few shots through his wretched craft!" "And I dare not," cried the captain. Just then Mark again caught sight of something which was taking place on the schooner's deck, not five hundred yards from where they pressed on in pursuit. It was hard to see at that distance, but he made out that a sturdy black was evidently renewing the struggle which had taken place before; but in spite of his efforts, he was being dragged to the side; then, to Mark's horror, a hand was raised and a blow struck, followed by a splash in the water, which was scattered far and wide, as the young midshipman closed his glass with his wet hands, feeling as if it had revealed horrors which he could not bear. "First cutters!" rang out, and the lad ran to the boat; the captain repeated his orders to the second lieutenant as the _Nautilus_ was run on, so as to get as near as possible to the drowning slave before her speed was checked and her boat lowered. There, all ready in their seats, the boat's crew waited. The expected moment came as the sails shivered, the boat kissed the water, the falls were unhooked, and in an extremely short space of time the _Nautilus_ was gliding on in full chase, and the cutter's oars were dipping in a quick, regular stroke which took them wide of the vessel's course, as she literally darted away. And now, as he stood up once more on the thwart, to try and make out the head of the black cast overboard, it struck Mark for the first time that they were alone upon the wide sea, and that the _Nautilus_ was very rapidly increasing her distance, while the schooner, to his excited fancy, already began to look small. But he had very little time for thinking. "Be ready with that boathook," shouted the second lieutenant. "Ay, ay, sir. Mustn't miss this one," muttered the speaker to himself. "See him, Mr Vandean?" "No, not yet, sir." "You ought to, by now. Watch for the rippled water where he is swimming." "That's what I am doing, sir," replied Mark, "but I can't see anything." "He's floating, perhaps. Pull away, my lads. Steady; we don't want to pass him." There was a few minutes' silence. "See him now, Mr Vandean?" said the lieutenant again, and Mark was silent for a few moments, as he scanned the surface round from beneath his hand. "No, sir, no sign of him." "Oh, don't say that, my lad. Look, look. We mustn't miss the poor fellow. Strikes me that we're going to pick up the whole cargo this way. Now then, wasn't that a splash yonder?" "No, sir, I can't see anything," said Mark sadly; and as he still eagerly scanned the surface amidst a breathless silence, only broken by the flapping of the water against the bows of the boat, it again struck Mark with a chill of awe that they were being left alone there; and he asked himself what would happen if the _Nautilus_ could not find them again.