Jack lowered himself over the edge of the boat, still holding to it with his hands.

"Yes, I'm ready," he said, "but--"

"Then dive!" cried Frank and pulled the trigger.

With a single movement he dropped the revolver into the bottom of the boat, and plunged deep into the sea himself.

CHAPTER VII

OFF ON A LONG CRUISE

At the very instant the lad disappeared beneath the water there was a flash of fire above the submarine, followed by a violent explosion-fearful, terrific.

The upper work of X-9 was blown high into the air and came down in splinters, scattered to the four winds of heaven. The deck was rent and open up with a great, yawning scam, through which the ocean rushed, driving the craft below the waves as though it had been drawn down by some mighty whirlpool. A minute later, where had been one of Germany's most terrible fighters, there was only a seething flood of water covered with floating wreckage.

The force of the explosion sent the water spouting high in the air like giant gushers. The sea boiled and lashed out angrily at what was left of the German craft. Not a living figure was to be seen upon the wreckage.

The deadly melinite had done its work.

Beneath the waters of the North Sea, where Frank and Jack had sought what shelter they could, the water tossed them about at will, in spite of their frantic efforts to hold themselves steady and remain below the surface.

Frank, not having time to take such a long breath as Jack, because of the suddenness with which he had dived, was the first to come to the surface. He was tossed high on the still angry waves, but by a Herculean effort, the lad managed to keep his head above water.

His first thought was of the small boat he had so recently left.

Glancing around, he saw it floating, bottom up, about a hundred yards away. He swam rapidly toward it; and as he hurried along, a head suddenly bobbed up directly in front of him.

It was Jack, struggling and gasping. Frank swam rapidly to him, and lent what a.s.sistance he could. Soon Jack was swimming easily with his friend toward the little upturned boat.

They laid hold of the little craft, and after a struggle, succeeded in righting it and clambering aboard, where they sat down, wet and weak, Then, for the first time, Jack turned his eyes toward the spot where so short a time ago had been the German submarine. He saw the ma.s.s of floating wreckage.

"Gone," he said simply, "and the poor fellows with it." He turned to Frank. "You certainly did a good job. I never knew that you were so handy with a gun."

"I am a pretty fair shot," Frank admitted modestly.

"But if you had missed the first time--?" began Jack.

"I couldn't miss," replied Frank quietly. "I knew that before I pulled the trigger. Some way, I felt certain the bullet would go true. Why, I hardly even aimed."

"Well," said Jack, "I'm sure I don't ever want you blazing away at me."

"I guess we might as well get away from this spot," said Frank.

"I wonder where we are?"

Jack stood up in the boat and looked long across the sea. Dawn was just breaking, and in the faint morning light he could see a considerable distance.

"No land in sight," he said finally, and sat down again. "At a guess, though, I should say we must still be off the coast of Holland."

"Yes; but how are we going to tell which way the coast of Holland is?"

"I'm sure I don't know. We'll just have to take a chance at it till the sun comes up, and then we can get our bearings. We'll have to be very careful though, for there are likely to be mines floating about. If we had some oars we could row a bit it would warm us up."

But no oars were in sight, either near the boat or among the floating wreckage.

"They must be at the bottom of the sea," said Frank, in some despair. "I should have thought to have made them fast."

"Never mind that," said Jack. "The question now is, what are we going to do?"

"Well, you know as much about it as I do," replied Frank. "What are we going to do?"'

"It looks to me as though we should have to drift and take a chance of being, picked up," returned Jack.

"Or be blown up by a floating mine," said Frank.

"That's a chance we shall have to take," said Jack calmly. "You should have thought of that before you bored a hole through that mine on the submarine."

Frank did not reply. At length he rose to his feet and took off his coat. Then he turned to Jack.

"Give me yours," he said briefly.

Jack obeyed without question.

Tying the two coats securely together, Frank loosened one of the thwarts in the little boat. He pulled some strong string from his pocket and soon had improvised a little sail. Then tying one sleeve to a cleat on one side and another sleeve to a cleat on the other he soon had his sail bellying before the stiff breeze.

"It's pretty low," he said, leaning back and surveying his work, "but it may move us along a little."

"How do we know we are going in the right direction?" asked Jack.

"We don't; but we might as well be moving as to stay here. We'll let her have her head and keep her steady as she goes."

Slowly the little craft, before the freshening wind began to make headway.

"This does beat lying still," said Jack. "I don't believe I would have thought of rigging up such a sail as that."

"I guess you would if I hadn't," replied Frank. "Now you try and take a little snooze, while I keep a lookout for a vessel of some kind."

"All right; only, you wake me up in a couple of hours and I'll stand watch."

Frank agreed to this, and Jack rolled over in the bottom of the boat, where, in spite of his wet clothing and the chilling wind, he was soon fast asleep. He was completely exhausted, and any kind of a bed would have felt good to him right then.

Frank, holding the rudder of the boat, sat silent, with his eyes scanning the distant horizon for the sign of a ship. But his watch was vain. Not even the smoke of a patrolling vessel did he see in the distance. His two hours of watch up, he shook Jack vigorously.

The latter was up in an instant, and soon Frank was occupying his place in the bottom of the boat.

For an hour Jack scanned the horizon without making out a ship; then, directly ahead, he saw a cloud of smoke.