the sides of the aperture striking his arms and shoulders as he went down.

Presently he landed on a hard deck, and was again carried a short distance. Here, when he was finally laid down, the coat was whisked from his face and he found himself in the blinding glare of an electric light.

Retreating footsteps came to him, followed by the slamming of a door.

As soon as his eyes had become used to the glow of the light, he discovered that he was in a small room with a curved iron deck overhead. An incandescent lamp was screwed into one of the walls, and there was a door in each bulkhead at the ends of the room.

Matt was bewildered by what had recently happened to him.

Had the crew of the Crescent resorted to violence in order to save Jurgens from capture? The law would take hold of the men good and hard for resisting an officer.

As Matt figured it, he had been brought aboard the sailboat. But what would his captors have to gain by a move of that kind? McMillan knew what the men on the Crescent had done for Jurgens, and it was a fair inference that the officer would soon pay the craft a visit, himself.

What put Matt in a quandary, however, was the fact that he could not reconcile his present surroundings with the Crescent. He was in an armor-plated room, and the sailboat was a small wooden vessel, and was hardly fitted with such a cabin as that to which the prisoner had been taken.

While Matt was wondering about this, a door in one of the bulkheads opened and another prisoner was carried in by two men and laid down beside him. This second captive likewise had his head smothered in a coat, but the blue uniform told Matt plainly he was the policeman. The officer was bound, just as Matt was, and as soon as he was laid down the coat was jerked away and the two who had brought him into the room started out.

"Wait!" called Matt, his voice ringing strangely between the steel walls. "What do you mean by making prisoners of us, like this?"

One of the men looked around and laughed grimly, but he made no other reply. The next moment the door had closed, and Matt and the officer were alone together.

"Here's a pretty how-de-do," fumed the officer. "These villains are goin' a good ways in their attempt to help that thief, Jurgens! Somebody'll smart for all this."

"Those men on the Crescent are foolish," said Matt. "It won't be long before McMillan gets us out of here."

"I don't know about that," was the answer. "Mebby it won't be so easy as you think for McMillan to get us away from these scoundrels."

"Where is McMillan? Do you know?"

"He was on the wharf with me, just before the Crescent got in. He thought him and me wasn't enough to get Jurgens off the boat, and so he went after another officer. You're Motor Matt, who's been making ascensions in that air ship—— I've seen you a good many times on the beach. My name's Holcomb."

"Where do you think we are, Holcomb?" Matt asked. "It can't be we're on the Crescent."

"Sure not. Looks to me as though we had been brought aboard Captain Nemo, Jr.'s boat, the Grampus. She bobbed up at the Inlet wharf yesterday. I'm on night duty at the Inlet, and I seen her last night."

"The Grampus?" echoed Matt. "She must be an ironclad."

"She's more'n that, Motor Matt. She's a submarine."

"A submarine! I haven't heard of such a boat being in Atlantic City."

"It ain't gen'rally known, I guess. Captain Nemo, Jr., is a queer sort of a fish, and he's invented a boat that he claims is a little better than any other under-water boat that was ever built. I talked with him on the wharf, last night. Who the cap'n is, nobody knows, and he hides himself under the name of Nemo, Jr. He talked straight enough, and fair enough, and allowed he was keeping quiet so as not to let reporters and other curious people bother him while he was in Atlantic City. It was your air ship that caused him to come here."

"The air ship?" queried Matt, more and more mystified.

"That's what he told me. Everything in the line of inventions, he says, interests him, especially if the inventions have anything to do with gasoline motors. This boat is run by a motor of that kind. Nemo, Jr., said he was goin' to take a fly with you to-day."

"I guess he didn't, then. No man by that name went up with us. But the point that's bothering me is, Holcomb, why were we brought here?"

"To save Jurgens, the movin'-picture man."

"How'll that save him?"

At that point the explosions of an engine getting to work echoed sharply through the steel hull of the Grampus. The whole fabric began to quiver, and muffled, indistinct voices could be heard. Immediately there was a perceptible downward movement.

"We're sinking!" exclaimed Matt.

"Looks like the scoundrels was takin' us to the bottom," said Holcomb grimly. "More'n likely McMillan has shown up with some more men and is makin' things lively for those on the wharf. The fellows that grabbed us are takin' us below the surface so the officers can't get at us, or Jurgens! Gadhook it all! Captain Nemo, Jr., didn't seem like a man who'd help out any underhand game like this. I reckon we're in for it, Matt. I ain't got any fears but that we'll come out all right in the end, but the outlook is a long ways from bein' pleasant. If Nemo, Jr., is trying'—— There! I reckon we've hit bottom."

Holcomb broke off his remarks abruptly. The downward motion of the Grampus had ceased with a slight jar. Before the two prisoners could talk further, one of the doors opened and Jurgens came into the room. He was followed by the man who had climbed out of the Crescent and had faced Matt on the wharf.

Closing the door behind them, the two men stood looking grimly down on Matt and the officer.

"I don't understand what your game is," cried Holcomb, angrily, "but if you know when you're well off, you'll set us at liberty, and be quick about it."

"You'll get your liberty, all right," said Jurgens. "Now that I've got hold of what I wanted, I'll not be long pulling out of Atlantic City. The moving-picture business can go hang for all of me! I've got a fortune in prospect, and I'll nail it here and now if it's the last thing I ever do."

"What do you mean by treating me like this?" demanded Matt; "what have I got to do with your plans?"

"You and the officer could have upset 'em mighty easy if we hadn't bowled you over and got you out of the way before the rest of those policemen got here."

"Is Captain Nemo, Jr., helping you in this game you're playing?" queried Holcomb.

"Helping me?" Jurgens turned to his companion from the Crescent with a husky, ill-omened laugh. "That's pretty good, eh, Whistler?"

"The best ever," answered Whistler, echoing the laugh.

"Townsend has helped me to the extent of furnishin' something I'd about given up laying my hands on," went on Jurgens, again turning his eyes on Matt and the officer. "I want you two to tell him that I'm off for the Bahamas, and that he'll have to get up in the morning if he beats Lat Jurgens."

"Townsend?" queried Matt.

"Yes," scowled the other, "Townsend. That's the name he uses when he's ashore. When he's afloat, he's Captain Nemo, Jr."

Matt was astounded.

"Have you stolen this submarine, Jurgens," he asked, "as well as that paper that——"

"You know all you're goin' to," interrupted Jurgens. Turning to Whistler he added: "Cut the boy loose and make him strip. It's time we got rid of him and the policeman and cleared out of here. We're a fathom under water, but Townsend may think of some way to get at us if we stay here too long."

Whistler bent over Matt and removed the ropes.

"You're going to put us ashore?" asked Matt, getting to his feet and stretching his benumbed limbs.

"We're goin' to send you to the surface, and you'll have to