would fight, for he knew that while there is life there is always hope.

Blindly and doggedly he continued his battle with the waves, peering into the northeast from time to time, in the hope of seeing the search light of the Grampus. He did not see the search light, but he saw something else lying sluggishly in the water not a great distance from where he was.

"A log!" he thought.

Under the impression that fate had thrown across his path a bit of drift from the mainland, he swam to the object and laid hold of it as it heaved and ducked on the placid waves.

It was not a log. As he put out one hand it came in contact with smooth, wet metal. The object was a long cylinder, blunt at one end and pointed at the other.

"A torpedo!" ran his thought, as he hung over the rounded object with one arm and supported himself in the water. "Who fired the torpedo?" was the question he asked himself.

He had leisure now for a little reflection. No strength was required to keep himself afloat, for the steel cylinder supported him.

As he hung there, lifting and falling with the long, deadly tube, his thoughts harked back to the queer object he, and Dick, and Carl had seen in the water. The result of his reflections paralyzed him.

Some mysterious enemy had launched the torpedo at the Grampus!

Had the infernal machine struck the submarine, the craft and every one aboard would have been torn to pieces.

A slow horror pulsed through Motor Matt's veins.

The same enemies who had launched the torpedo must surely have jerked Matt from the deck of the submarine. But who were they? where were they?

With difficulty he lifted himself and got astride the rolling cylinder. From that elevated position he looked around him into the darkness. Silence reigned in every direction. There was no sign of the mysterious foes who had attempted to destroy the Grampus and to make a prisoner of her commanding officer.

Presently the young motorist became conscious that the coil was still about his throat, and that a long object was trailing downward and hanging with some weight from his neck.

It was a rope. He began pulling it in, coiling the wet length of it in his hand. The rope was all of seventy-five feet long, he judged, and that distance must have marked the position of his foes when the noose was cast. To see even half that distance into the thick darkness was impossible, but why had Matt not been able to hear the men who had attempted such dastardly work?

Speculations were useless. Matt, however, had secured a makeshift raft which would keep him afloat until such time as the Grampus, or some other boat, could pick him up.

Hoping that the submarine would come to no harm, and determined to make the best of his desperate situation, the king of the motor boys set about making an examination of the steel tube that supported him.

CHAPTER III.

SAVED BY A TORPEDO.

Matt's first move was to take the noose from about his throat and pass the rope around and around the torpedo, tying it fast. The loops of the rope gave him a handhold which he could not possibly have secured otherwise on the hard, smooth shell, rendered slippery by the water with which it was drenched.

The torpedo, he quickly discovered, was a Whitehead—a powerful and deadly engine in use by all the navies of the world.

It was about seventeen feet long and a foot and a half in diameter. Torpedoes of this nature are constructed to run under the surface at any required depth down to twenty feet. A propeller and compressed air furnishes the motive power, and as the air becomes exhausted, the torpedo rises higher and higher. With the air shut off and engine stopped, the cylinder rises to the surface. As that was the case in the present instance, it seemed certain that the motive power of this particular torpedo had been nearly exhausted.

The Grampus, being constructed for work in time of war, had torpedo tubes and one torpedo aboard. Matt had studied the mechanism of the Whitehead, and he was able to proceed intelligently in his present dilemma. If there was still any air in the big tube, he might use it to carry him to the north and east, in the direction taken by the Grampus.

The lever, he discovered, which locked the engine was standing erect, while the "tripper," which worked automatically the instant the torpedo was discharged and put it under its own power, was lying flat on the curved side.

Before trying to get the compressed air in the shell to working, he swam to the blunt end of the torpedo and removed the small propeller that manipulated the firing pin. By this wise move he rendered harmless the explosive within the shell.

Swimming back, he mounted his queer raft by means of the rope loops, lifted the "tripper," and depressed the starting lever.

The twin screws, placed tandem fashion at the stern, began slowly to revolve. Heading the point of the tube north by east, he began one of the strangest rides that had ever fallen to his lot.

As the air within became more and more depleted, the steel cylinder rose higher and higher in the water.

For a lad so deeply in love with motors as was Matt, the novelty of that ride could not fail to appeal to him. He was safe, at least for a time, and felt sure that ultimately he would gain the shore or be picked up by a coastwise ship. As for the Grampus, there were cool heads and steady nerves aboard of her, and the submarine's safety would be looked after. Besides, the mysterious foes had failed in their night's work, and there was probably no more danger to be apprehended from them.

As Matt held himself astride his queer craft, guiding it by a pull this way and that, he fell to thinking of the manner in which he had been hurled into the sea.

Some boat had discharged the torpedo, and it seemed certain that those who had tossed the rope over his head and pulled him from the submarine's deck had been on the same boat.

Had it been the intention of Matt's enemies to haul him aboard their boat, or only to strangle him and keep him in the water until the Grampus got well away, then cast him off and let him sink to the bottom?

Matt's humane instincts rebelled against the latter supposition. His enemies, he reasoned, had intended hauling him aboard their boat, but in some manner had lost hold of the end of the line.

A Whitehead torpedo costs something like four thousand dollars, and is altogether too valuable to leave adrift when it has been fired and misses its target. Those who had discharged the torpedo would surely look for it—and, if they found it, they would also find Matt.

This caused the young motorist a good deal of trepidation. He reasoned, however, that on account of the darkness of the night and the fog, his mysterious foes would probably remain in the part of the ocean where the torpedo had been fired and look for it in the daylight. Between that hour and daylight, Matt was hoping to be picked up.

The compressed air in a torpedo will carry it about nine hundred yards. This torpedo had not gone its full distance, on account of an automatic misplacement of the "tripper" and starting lever, but enough of the air had been used so that Matt's ride was a short one.

After a few minutes the propellers ceased to revolve, and Matt and the steel cylinder came to a stop, heaving up and down on the surface of the water. Yielding to the pull of the current, the torpedo started erratically seaward, and another fear was born in Matt's mind.

The farther seaward he was carried, the more difficult it would be to fall in with a passing boat, and the farther off would be his rescue. To carry his grewsome thoughts still farther, there was a good chance that he would succumb to thirst and hunger before his woeful plight was discovered,