"Ha, ha! Ho, ho!"

There could be no question that the unknown was merely playing with him.

Little as he liked to make the ugly throw Harry knew that he had to do it.

When Hazelton had anything to do he believed in doing it well. So, putting all possible force into his throw, Harry let the rock fragment fly, and this time he was sure that his enemy would not be able to dodge in time.

Nor did the black man make any seeming effort to dodge.

b.u.mp! Squarely in the black face the rock landed. Harry heard the sound and felt ill within himself. Yet the black man did not stagger. With a contemptuous snort he kicked the fragment of rock into the water as it landed at his feet.

"Ha, ha! Ho, ho!"

For the first time Harry Hazelton felt positively dismayed. He saw the long, ma.s.sive arms moving, looking like a powerful ape's arms. There could be no doubt that the unknown was ready for a spring.

Harry did not retreat. Where could he run to? Only a few yards could he go out towards the end of the wall. Then, if he wished to continue his flight he could only take to the water.

Only a glance was needed at the bulky, powerful frame of the unknown to make it appear certain that the latter could swim two rods to the young engineer's one.

Harry decided instantly to stand his ground and to make the most valiant fight possible on so slippery a footing as that presented by the top of the retaining wall.

"Ha, ha! Ho, ho!"

It was as though the black unknown sought to terrify his intended victim with his repet.i.tions of that harsh, discordant laugh. Harry braced himself and waited.

Then, off sh.o.r.eward, came the sound of "put-put-put." The motor boat, "Morton," was putting out at last.

"If I can keep this fellow busy for a few minutes, I can have all the help I want," flashed through Hazelton's mind. So he opened his mouth, raising his voice in a long, pent-up hail.

"R e---e---e a d e! To---o---o---om R e a d e! Quick! Hazelton!"

"Ha, ha!" jeered the unknown black.

Then, suddenly, he leaped---not unexpectedly, however, for Harry had been watching, cat-like.

The unknown threw out his arms, seeking to wrap them around Hazelton.

Not in vain had Harry been trained, season after season, on the athletic ground of one of the best high school elevens in the United States.

As the fellow leaped at him Harry crouched lower and went straight at his opponent.

Powerful as the stranger was he was no football player. Harry "tackled"

him in the neatest possible way, then strove to rise with this great human being.

In the first instant it seemed to the young engineer as though he were trying to lift a mountain. His back felt as though it were snapping under a giant's task. Yet, but for one fact, Hazelton would have risen with his man, and would have hurled the mysterious one over into the waters of the gulf.

Just in the instant of victory Harry's injured right foot gave out under him. With a stifled groan he sank down just as he threw his opponent.

The black, instead of going into the water, landed hard on his back on the top of the wall. He was up again, however, before Hazelton could repress the pain in his foot and leap at the wretch.

"Ha, ha! Ho, ho!" came the tantalizing challenge.

"Put-put-put!" sounded over the water, coming nearer all the time.

"Re---e---e---e a d e! T o m R e a d e! Help---quick!" yelled Harry, l.u.s.tily.

This, doubtless, was the first call that Tom, at the bow of the motor boat, thought he heard.

Uttering a snort, this time, instead of the laugh, the black sprang at his intended prey. Their heads met, with considerable force. Then, with a wild chuckle, the black wound his apelike arms around the young engineer.

"Reade! Tom Reade! Reade!" bellowed Hazelton l.u.s.tily, as he tried desperately to free himself from the crushing embrace of the other.

Over the waters came the penetrating beam of a small search-light. The "Morton" was coming nearer all the time, but the ray did not yet reach with any great clearness the point where Harry Hazelton had been fighting for his life against his strange foe in the black night.

"Keep parallel with the wall, Evarts," Tom ordered, crisply. "Conlon, are you pushing the engines for all it's worth?"

"Yes, sir," came from the engine-tender. "This old craft isn't good for quite seven miles' an hour, anyway."

"There! Now I've picked up the part of the wall where there isn't any wall in sight just now," said Tom, wincing over his own bull. "Hazelton ought to be just this side of there."

"There's no one near the breach," replied Evarts.

"So I see," Reade admitted, in a tone of worriment. "Oh, well, Harry isn't such an infant as to be wiped out all in one moment."

"Where is Mr. Hazelton then?" inquired Evarts, as Tom swung the arc of the searchlight in broad curves.

"Great Scott! I wish I knew!" gasped Reade, his perplexity and his anxiety growing with every second. "There appears to be no one on top of the wall."

Evarts ran in within a few feet of the wall, on the sh.o.r.e-side of the breach.

"Shall I land you there, sir?" questioned the foreman.

"Presently," Tom nodded. "But now, back out a few feet and swing the boat's nose around so that I can make a search with this light." Evarts obeyed the order. Despite the smallness of the light, Reade was able to send the searching beam of light back nearly one-half of the way to sh.o.r.e.

Nowhere was there any human being visible on the wall.

"Harry! Hazelton!" bawled Tom, with all the power in his lungs.

There was no answer.

"Jupiter! You'll have to land me, I reckon," quaked Tom Reade. "Drive her nose in---gently. I'll be ready to jump."

"Be careful how you _do_ jump," warned Evarts. "It's mighty slippery on that wall tonight."

Tom poised himself as the boat moved in close. Then he took a light leap, landing safely.

Here the young chief engineer again brought his pocket flash lamp into play. Closely he scanned the top of the wall all around where he knew he had left his chum.

But Harry was nowhere to be seen, nor, on the wet wall, could Tom find any signs of a scuffle, or any other sign that gave him a clue.