"It's plain to be seen that we'll not get much help from any ship on the North Sea!" declared Jack at length, as the ballast tanks were found to trim the vessel. "They're scared of us, I believe!"

"They haven't any reason to be scared of us!" stoutly protested Jimmie. "We have never done a thing to them. We're absolutely neutral!"

"It seems to be one thing to be neutral," laughed Ned, "and quite another thing to convince other folks of the fact!"

"They might at least have given us a chance to explain!" grumbled Jimmie. "We had a white flag flying for them to see!"

"Yes," argued Ned, "but did you stop to think that we were showing ourselves in a bad light? Remember the newspaper accounts of all the damage done by a submarine? I'm not surprised they ran away."

"And then we come along in a submarine! Of course, we couldn't expect them to wait for a German undersea craft to come popping out of the ocean and waltz up alongside so they could say: 'Good morning, Mr. Dutchman! Won't you please accept this fine ship?'" added Jack.

"Well, I'm it!" declared Jimmie, joining in the laugh that followed Jack's facetious remark. "The joke's on me, all right! If I hadn't painted that figure 'three' in the name, we would have been on our way to England by this time! Oh, well," the boy added, "we'll get to England before long, anyhow, so I should worry!"

"It all shows, boys," spoke up Ned, "that we've got to be mighty careful about our appearance and the company we keep. We have gotten into this scrape largely because we were found in possession of goods we had no business to have. This last incident came about because we pretended to be something we were not!"

"I think that ought to be a good lesson to us," stated Jimmie. "It will be for me, I know! I'm sure I'll take it to heart!"

"I'm mighty glad we're away from that inquisitive gunboat!" put in Frank. "Now, what's the next thing for us to do?"

"I move that we keep below the surface for a while. If we hold on a general southeasterly course, as has been suggested, we can't fail to bring up somewhere on the English coast."

"That sounds like the most reasonable plan," agreed Frank. "I propose that we put on speed and hurry along. Let's get somewhere!"

"Here we go!" cried Harry, increasing the speed with a touch on the levers. "Let's keep a sharp lookout, though!"

About half past three o'clock the boys decided to rise to the surface for the necessary airing of the vessel and storing of another supply of fresh air in the tanks provided for that purpose.

In furtherance of this plan, the rudders were shifted while Harry slowed the engines. Directly the craft ascended. The gauges indicated a depth of about eight fathoms when Jimmie, who was at the helm, requested that the rudders be again deflected.

"What's the matter?" questioned Ned, stepping forward.

"I can see the light reflected down through the water, and there's a big shadow up there!" declared Jimmie.

"What do you think it can be?" asked Ned wonderingly.

"Probably it's a big vessel of some sort. It may be a war ship, or it may be only a cargo carrier. In either event I don't want to get tangled up in the propellers. Let's sheer off a bit."

"All right," agreed Ned. "I'll go to the periscope. Maybe I can find out something as we rise slowly to the surface."

Cautiously creeping nearer the surface, the lads put the periscope into action. By its aid Ned made out that the craft was an armed vessel. The new "U-13" lay just submerged about a ship's length to starboard of the stranger. They maintained about the same speed.

Ned declared that he could make out the British flag at the stern of the other vessel. He stated that he could also notice a number of people aboard the steamer.

"Can you see what they look like?" asked Jimmie.

"They are regular sailors and marines," answered Ned. "Why," went on the lad excitedly, "that looks like Mackinder at the rail!"

Curiously the others crowded about the object glass of the periscope. Each declared in turn that they recognized Mackinder.

"Now, I wonder what he's doing aboard that vessel!" mused Jack.

"Quite likely this ship met the fishing boat and took him off so as to save the other the trouble of going clear back to England!"

"No doubt that's it," agreed Jack. "But look!" he continued, "he's discovered us! See him pointing toward us!"

"Better get ready to dive, then," cautioned Harry. "If he's able, he'll get them to shoot at us. If they hit the 'U-13' it'll be a long way to Tipperary for us! We don't know how thick this armor is!"

"Down we go!" shouted Jimmie, seizing the wheel. "Lively, now!"

Even as the boy spoke, a muffled roar was distinctly heard by the lads in the submarine. A crash that reverberated through every portion of the vessel told that they had been hit by a projectile.

With a quick, startled glance at his companions, Ned hastened aft to examine the possible damage. He could discover no leak.

"I guess we're lucky, after all!" he stated presently. "We're not taking in water, so I'm sure they didn't do very much damage."

"It might have been more serious, though!" commented Jack.

"Maybe the shot just carried away some of the light work like railings and so on around the deck. I don't think the shot struck the hull, or we'd have heard more racket," went on Ned.

"Let's keep below the surface for a while. Maybe we can get away from those fellows far enough to be out of their sight while we change air. They're not the least bit sociable!"

"Full speed ahead, Harry!" cried Frank. "Let's hurry on!"

"Better take it easy," cautioned Jimmie. "We may not be out of the woods yet. Let's just go along slowly for a while."

"Aw, go on!" scorned Frank. "What's there out here to bother?"

"Sure!" chimed in Jack. "We're away out in the North Sea where we can find nothing but warships and sailing vessels and such!"

"Maybe we might run into the real 'U-13'," countered Jimmie. "Then, what would you do if you should meet that fellow?"

"Why, put on steam and run away from him, of course!"

"All right, go ahead if you want to," submitted Jimmie unwillingly, "but I don't think it wise. It's taking considerable risk!"

Since the majority seemed to be in favor of more speed, the engines were again urged to greater effort. Suddenly all were startled by a cry from Jimmie. The boat swerved sharply to starboard, rolling until the deck was at an acute angle. Harry reached for the levers, prepared to stand by the engines for orders from the pilot.

Directly Jimmie rang a stop bell. The vessel came again to an even keel. The boys were once more able to stand upright.

"What's the matter, Jimmie?" cried Ned, as he scrambled to his feet. "Is it a whale, or did you nearly have a collision?"

"Collision is exactly the word!" declared the other. "I saw the masts of a ship standing right in our path. I got this little craft turned just in time! That's what we get for blundering along so fast!"

"What kind of a ship is it?" asked Frank, peering from one porthole after another. "Are you sure it was the mast of a vessel?"

"Why, certainly, I am sure!" was Jimmie's decisive answer. "Don't I know a ship's masts? I surely do!" the lad answered his own question.

"Let's swing around and see what it was," proposed Frank.

"All right, turn the deflecting rudders and down we go!"

Swinging in a broad circle, the submarine was directed downward to a level equal with that of the hull of the ship, whose masts had so nearly proven disastrous to the boys. As the craft sank deeper the crew watched with a great deal of curiosity from the thick glasses over the portholes. Carefully they studied every detail of rig.

Although the sunshine penetrated to some distance below the surface, they found that at the depth where the hull lay a semi-twilight prevailed. The upper portions of the masts had been clearly visible, but the decks lay in a haze that prevented their seeing well.

"Looks like the ship is almost new!" stated Frank.

"Possibly it has been sunk only a short time," ventured Jack.

"Can you make out what ship it is?" asked Ned.

"Wait a minute until we pass the stern again," said Frank.

"I can see it!" declared Harry in a moment. "It's the Wanderer of Sydney! That will be an Australian vessel!"

"And that great gap in the port side indicates that the sinking was the work of our namesake!" stated Ned. "This is another victim of the German 'U-13'. Probably it is only one of many!"

"No wonder the other fellows don't seem inclined to be any too sociable!" said Jack. "They really cannot be blamed!"

"Right you are, Jack," responded Ned. "When anyone hits at the pocketbook we're apt to consider everybody under suspicion."

"Let's get closer and examine the damage done by the torpedo," suggested Frank. "I'd like to observe the effects of the attack."

Shortly the misnamed "U-13" was creeping alongside the hull of the sunken vessel. Jimmie handled the wheel dexterously, ever alert for possible danger. Harry stood by the engines, ready at a moment's notice to assist in executing any maneuver desired.

"Looks as if the whole side of the ship had been torn away," stated Ned, as the submarine crept slowly past the jagged wound.

"Those torpedoes surely are powerful," agreed Frank. "I hope everybody got away from the ship before the explosion took place."

"They probably gave the crew plenty of time to escape if this is the work of the 'U-13'," commented Ned. "You say they gave the crew on your vessel ample time to get safely away?"

"Yes, but the men let themselves become panic-stricken. They lost their heads and consumed a good deal of time. Besides that, they forgot they were civilized. One of them hit me an awful clip."

"And pretty nearly left you on board to be drowned!"

"These fellows did the same thing!" announced Jack, peering out.

"Did what?" queried Ned, wondering what the other meant.

"Left a man aboard when the ship sank," stated Jack, pointing through the little port hole. "There he is, walking about!"

Clearly the boys saw a figure apparently crossing the deck.



CHAPTER XVII

ALONE AND HELPLESS

"Good night!" almost shrieked Frank. "That's uncanny! Whoever heard of a man walking about at the bottom of the ocean?"

"Where did he come from, Jack?" asked Ned.

"I saw that figure come out of the companionway," stated Jack. "I thought I was mistaken at first, because of the dim light. I looked again as you boys were talking. Then I saw that it was the figure of a man, apparently. He seems to be carrying something in his arms!"

"There he goes over the side of the vessel!" whispered Harry in an awestruck voice. "What sort of deal is this, anyway?"

"Did you notice the knapsack thing he was wearing on his back?" asked Frank. "If I was superstitious, I'd say it was the ghost of a soldier who had been drowned and was seeking his way back home!"

"We don't take any stock in that ghost business!" declared Ned stoutly. "Some things may look supernatural because we don't understand them, but there's always an explanation if we seek it!"

"What is your explanation of this thing, Ned?" questioned Jack.

"Probably some mass of seaweed or some other substance got caught in a current and lodged against the cabin on the Wanderer. When we circled about the wreck we set up counter currents that may have released this mass. It then floated along in the current to finally sink on the other side of this submerged hull. That's all there is to it!"

"I wonder what sort of a current is bringing the bloomin' thing back again!" announced Jack as Ned concluded his explanation. "It's moving its lower edges most remarkably like a man walking!"

Ned's look of bewilderment increased. Clearly the boy was puzzled. Even he, himself, was not quite satisfied with the explanation of the strange sight which had greeted the boys.

Slowly forging ahead, the submarine passed toward the stern of the Wanderer, shutting the strange figure out of sight.

"Turn around the stern again, Jimmie," requested Ned. "Go easy on the engines, and we'll have a look from a new angle. This is getting rather spooky, I must say. I want to examine into it!"

Again the false "U-13" rounded the stern of the wreck. Slowly the craft nosed along the port side to a point abreast the mizzen chains. Directly at a signal from the pilot, Harry shut off power altogether.

The strange magnetism that seems to exist in all objects at sea slowly drew the submarine toward the ship. Its drift had been sufficient to bring the vessel to a point abreast the main rigging before it stopped.

By this time the craft had approached close to the wreck. A very slight jar told the boys that their vessel had touched the other. Eagerly all watched from the portholes, now but a short space above the level of the rail across which they looked. Directly all was still. At this depth, no movement of water was discernible.

Feeling awed by the strangeness of the situation, the boys refrained from speech. They watched for the reappearance of the strange figure.

Soon Jimmie hissed a warning. He reached out a hand to turn the switch controlling the lights. The boat lay in utter darkness.

A figure stepped out of the Wanderer's companionway.

It appeared to be that of a person of medium build. The boys could now see that it was clothed in what seemed to be a diver's suit. The helmet, however, was not connected to any air pipe. Neither was there a line leading upward to indicate the presence of assistance. A hump on the shoulders, giving the impression of a knapsack, afforded much wonderment and increased the mysterious look of the newcomer.

"Sh-h-h!" warned Ned in a sibilant hiss, as the figure came directly toward their position. "Keep quiet!" he whispered.

A few steps carried the stranger to the rail. The boys saw him give a start of amazement as he prepared to go over the side of the ship. Clearly the strange diver was surprised to see the craft in that position. He stepped back a pace, then came gingerly forward.

Evidently the man was astonished to observe the "U-13". He climbed slowly into the main shrouds. From that position he surveyed the craft more completely. Again he returned to the deck.

During this examination the lads had remained quietly at their posts, not caring to make their presence known until they were sure of the identity of the other. They still remained with their faces at the portholes, where they observed, so far as possible, every move of the stranger.

Directly they observed the diver pick up the burden he had brought from the cabin. He hastened to the rail of the wreck. In a moment he had clambered overboard, letting himself down by means of a line secured to a belaying pin at the mainmast.

"That's funny!" observed Ned, as the other disappeared from view. "What do you suppose made him scuttle out of sight so hurriedly?"

"Maybe he, like the warship, saw our name—'U-13'—on the side of the vessel!" ventured Jimmie. "They all run away from that!"

"It surely doesn't make us many friends!" declared Ned.

"You're right!" answered the other. "It's the original killjoy!"

"Let's dive a little deeper," suggested Jack. "Perhaps we can find out where this new chap is going with those bundles."

"Perhaps we'll find out how he got here!" added Frank.

"And while you fellows are 'perhapsing'," put in Jimmie, "I'll say that perhaps we'd better stick out! Perhaps he doesn't want us nosing around his property, and perhaps he'll touch off a bomb!"

"What's the matter with you lately?" inquired Frank. "You're getting to be a regular little 'fraid-cat'! You never used to be so timid about sticking your nose into other people's business!"

"I'm not afraid to go looking into things now, only I've got a hunch that we'd better not do it, that's all!" answered the lad. "Just because I happen to want to leave a fellow alone is no sign I'm a 'fraid-cat'. If you lads want to go anywhere, you tell me the name of the place. I'm game to stick with you until they turn out the lights!"

"Spoken like a man, Jimmie!" declared Frank. "That sounds like the old Jimmie we used to know. Now, let's go down a ways."

Harry sprang to the levers. A few shifts of the control brought the storage batteries to work operating the pumps. With the additional water admitted by this process, the false "U-13" sank until far below the level of the rail of the wreck. Still deeper and deeper it settled.

Presently the boys at the port holes could discover the bends of the sides, indicating that they were nearly to the ocean floor. In another moment a slight bump told them that the craft rested on bottom.

"I saw a flash of light just now!" stated Jimmie.

"Where did it come from?" asked Ned, stepping forward.

"Just ahead of us on this side of the ship. The shadow lies heavily there, so I can't make out what's located in that place!"

The boys had not long to wait, however, to discover the cause of the flash which Jimmie had seen. Almost following the boy's words came a dazzling beam of light, piercing the dark shadow like an arrow. For a moment the boys were blinded as the searchlight's flame played on the forward part of their vessel.

Presently the light shifted. It was turned against the side of the sunken Wanderer. Up and down the light traveled, revealing the rugged sides of the hull, with its covering of barnacles below what had been the water line. Outward the beam went, showing nothing but ocean floor. Fishes were illuminated and dazzled by the strong ray.

Finally the light returned to the false "U-13", where it settled for a moment. Directly the light was turned off.

Jimmie had been shading his eyes with a protecting hand. He was, therefore, not so much blinded by the glare as the others had been.

"There they go!" he cried, as the light was removed from the port hole through which it had been shining. "They're rising!"

"Who can it be, I wonder?" questioned Ned.

"I'll never tell you!" declared Jimmie. "Oh, yes, I will, too!" he amended his statement. "If you want to know, it's the 'U-13'!"

"The 'U-13'?" questioned the lads in chorus.

"The 'U-13'!" positively stated Jimmie. "Here," he cried, turning a switch leading to the searchlight. "Take a look!"

The powerful storage batteries on the vessel occupied by the boys generated a ray of light that pierced the darkness of the undersea world with ease. Sharply outlined in the circle of flame the lads clearly saw the form of a submarine vessel similar in many respects to their own. There was the same sharp prow, the same tapering stern with conning tower, keel, port lights, and every essential feature of the vessel upon which they were located.

Outlined upon the side, in letters fully the same size as those upon their own vessel, the lads saw distinctly the mark "U-13."

"What do you know about that?" gasped Frank. "That's fierce!"

"Is it the same vessel you saw off Land's End, Frank?" asked Ned.

"I'm sure I can't say," returned the other. "I think it is! Of course, we're somewhat below it. Besides the difference in perspective from this angle the water has a great deal to do with changing the appearance of everything. The general outlines appear similar, however."

"Then we're in a ticklish position!" declared Ned. "Suppose those fellows take it into their head to torpedo us?"

"If they do," stated Frank decisively, "they'll play havoc!"

"They're going over the wreck!" stated Jimmie in a whisper.

"Let's rise a little and see which way they head for," proposed Frank. "We can then go in the opposite direction for a while."

"I think we'd better slide right along to the southwest," stated Jimmie. "I know I'm meeting a good deal of opposition, but I've a hunch that we'll be better off if we get right away from this spot!"

"Been reading that dream book again, little man?" asked Ned, with a laugh. "Sorry, Jimmie, but the majority seems to be against you!"

"All right, Boss!" returned Jimmie with a smile. "I'm game to stick with the bunch! You'll find me right here smiling all the while!"

"Jimmie," gravely stated Ned, "I wish we could all get some of that sunny disposition of yours. We need a lot of your optimism."

"Thanks!" was Jimmie's reply, delivered with an excess of politeness. "Now, I'm at the wheel, Captain. Where to, sir?"

"Let's rise first and see what the other is doing!"

"Ding, ding!" cried Jimmie. "Touch up the mule, Harry!"

Harry's manipulations of the levers brought the false "U-13" rapidly to a level with the Wanderer's deck. Through the port lights the boys could see the other submarine across the sunken ship. It seemed to be gradually descending toward the bottom.

"Let's follow them and see where they go!" proposed Jack.

"At your service, sir!" cried Jimmie, saluting. "We'll proceed to proceed!" he added with a grin. "Here goes after the real 'U-13'!"

"Go ahead slowly, Harry," cautioned Ned. "We don't want to overtake them yet. We're in the shadow here, so they probably won't see us if we hang back a little. Just give the wheel a little kick."

Slowly the vessel carried the boys over the sunken Australian. They were passing between the main and mizzen rigging at a level slightly lower than that of the main yard.

"What's that just ahead of us?" queried Jack, at the porthole.

"I don't see anything," replied Ned. "What and where is it?"

"Right here," declared Jack, pointing. "No, you're too late! I thought it looked like a snake in the water at first, but I see it was only a piece of rope hanging from the rigging. It's all right!"

"Possibly it has been hanging down all the time but the current caused by the passage of the other vessel swung it outward," ventured Ned. "It will no doubt slip past in a moment!"

But this prediction was not fulfilled. With a sudden lurch, the stern of the false "U-13" rose, tilting the deck sharply forward.

With a groan the propellers stopped.



CHAPTER XVIII

HELP FROM A STRANGER

Harry uttered a sharp cry as he stumbled forward along the steep incline of the floor. It seemed as if some huge power had grasped the stern of the craft, raising it until the vessel tilted forward at an angle which rendered walking impossible.

All the boys were thrown toward the forward end of the vessel, where Jimmie was located. Ned and Jack lost their footing. They rolled awkwardly to the forward bulkhead. Harry and Frank managed to remain upright by hurriedly grasping at parts of the machinery or at stanchions. Their progress was undignified as well as sudden.

"What's up?" sharply questioned Jimmie, regaining his feet.

"The stern's up!" facetiously replied Jack, also struggling to a standing position. "Is anybody hurt?" the boy continued.

A brief examination disclosed the fact that beyond a few minor bruises none of the boys had been seriously injured. Their first care was for each other. All were glad to find no one badly hurt.

"What on earth can have happened to us?" asked Ned, peering from a port light on the starboard side. "Did we collide with something?"

"I don't believe we did," returned Harry. "There wasn't any bump as if we'd run into another object. We just stopped!"

"And then the stern went up into the air and stayed there!" put in Jack. "Something's got us by the stern and won't let go!"

"I think I know what it is!" announced Frank. "What is it they call these fishermen with a big net dragging around?"

"Fishermen!" answered Jimmie, with a grin.

"Stop your nonsense!" ordered Frank, administering a friendly punch to his red-headed comrade. "I mean the fellows with a big drag net!"

"Trawlers is the word you want, Frank!" said Jimmie.

"That's it!" agreed Frank. "I'll bet we're tangled in one of their nets. Maybe we can't get loose again, either," he added.

"Don't you believe it!" scorned Jimmie. "If it was a fisherman had hold of us, we'd be yanked around pretty lively. I think it is that rope we saw hanging in front of the port light!"

"I believe you're right, Jimmie!" Ned put in as he gazed through the heavy glass on the port side. "I can see that we're swinging close to the mainmast. There is no motion to the boat, so that makes me think your solution is about right. Now to get loose!"

"Yes, I agree with you!" stated Harry. "But how? If your assumption is correct, we've got a big piece of line wound around the outboard end of the shaft. It is probably more or less tangled up in the propeller also. We can't turn the engines over!"

"Maybe we could throw out the clutch and turn the shaft backwards enough to unwind the line!" suggested Frank.

"I'm in favor of rising to the surface if the slack of line will permit," offered Jack. "We could then open the hatchway. It would be easy enough from there to clear the line from the screw."

"That's probably the best way out of it," commented Ned. "Suppose we try that. Harry, can we rise as Jack suggests?"

"I don't know," came Harry's hesitating reply. "I'll try!"

Accordingly the boy clambered from his position near the forward bulkhead to the compartment amidships, where the pumps were located. A shift of valves followed by a touch on the levers connecting the storage batteries with the electric pumps started the process of emptying the ballast tanks.

Almost instantly the forward end of the craft began to rise. Very shortly the deck was in a level position. Then, as Harry continued to empty the water ballast, Frank and Ned, assisted by Jimmie and Jack, threw the clutch on the propeller shaft out of contact in order to permit the tail shaft to turn without moving the engines.

They then endeavored to turn the portion of the shaft which projected through the stern bearing in the back up motion to free the propeller. They hoped thus to release the rope which they believed to be wound around the outboard portion of the shaft.

Strive as they might, however, the shaft stubbornly refused to move. Their utmost efforts were unavailing.

At length, out of breath and exhausted, Ned sank back upon a locker. He looked at his companions with a curious expression.

"What's the matter, Ned?" inquired Jack anxiously. "Are you ill?"

"I feel badly, boys," replied Ned. "Unless we can devise some means to free that line from the shaft, we are in a pretty tight fix!"

"How near the surface can you bring the boat, Harry?" asked Frank.

"The gauges show that we're about two and a half fathoms down at present," replied Harry. "I have pumped a lot more water out than would ordinarily be required to bring us to the surface."

"Then we must be held by that line!" declared Ned.

"Let's try some other maneuver with the ship before we give up!" put in Jack. "We're not half though our experiments yet!"

"All right, what'll you try?" asked Ned in a despairing tone.

"I don't know," was the answer. "But we're going to do something to help get us out of this fix. How would it do to fill the tanks to sink us as far as we can go? Then we could empty them in a hurry, which would make the boat rise swiftly. The jounce would perhaps break the line and let us up so we could get some fresh air."

"If we don't get some fresh air pretty soon, we'll have to do something desperate. The reserve tank is nearly exhausted!"

In compliance with Jack's suggestion, the ballast tanks were again filled. Gradually the "U-13" descended to the bottom. As the deck began to tilt forward, as it had done when the craft was first stopped, Harry threw into operation every pump that could be used to empty the water from the ballast tanks. The boat rose rapidly.

With a jerk that nearly threw the boys off their feet, the "U-13" came to a rest. The gauges still showed the same depth as before.

Ned's face turned ashen as he sank upon a locker. The others gathered around him, expressing sympathy. The boy was clearly distressed.

"Never mind, Ned!" spoke up Frank. "We're coming out all right! The only trouble is that we haven't tried the right thing yet!"

"But I can't seem to think of a thing to do in this case," protested the other. "I'm all out of ideas! I'm sorry that we tried to follow that other submarine. I wish we had taken Jimmie's advice!"

"Never mind that now, Ned. We're close to the surface. If it becomes necessary, I will volunteer to be shot out of the torpedo tube. I can rise to the surface, swim about until I get my wind again, and then dive and cut the rope. That will release the whole ship!"

"Jimmie, that's awfully good of you to offer that, but I feel that I should be the one to do it," was Ned's reply.

"No, sir!" declared Jimmie promptly. "You're in no condition to attempt anything like that. You're worried, and your heart action is not right just now. My mind is a blank, and my heart is as sound as a bullet! I'm just the one for the job!"

As if the matter were understood, Jimmie began divesting himself of his clothing. He deposited his jacket on the locker beside Ned.

"Harry," he said, turning to his chum, "will you see that the torpedo tube is connected up and in working order? You might try a discharge for practice. We can spare a little of this air!"

By the time Jimmie had stripped and secured a knife to a belt about his waist, Harry pronounced the tube ready for operation.

"Now, fellows," said Jimmie, shaking hands with his chums, "there's about one chance in a million that I won't get through this all right. If you are not up to the surface in five minutes, you may know that I've failed. Then you'd better send out another lad!"

"Me next!" shouted Jack, beginning to remove his shoes.

Harry was peering from the heavy glass protecting the forward porthole. As Jimmie stepped forward to enter the torpedo tube, Harry held up a warning hand. He turned an anxious face to his friends.

"There's something outside here!" he announced in an anxious tone. "I saw it once, but didn't get a clear view!"

"What did it look like?" asked Jimmie. "Is it alive?"

"I'm not sure, but I think it's another submarine!"

"Probably the real 'U-13' come up to look us over. Never mind those fellows. I'm going ahead and cut this wagon loose!"

"Wait a minute!" cried Ned. "I see the craft over here to starboard. It's a peculiar vessel, too! I think I see a man!"

"I see him, too!" declared Frank from a porthole a short distance aft. "Do you suppose he's trying to get us to descend again?"

"Maybe that's it! Let's try it, anyway!" offered Harry.

"Go ahead!" agreed Ned in a tone that showed he was again taking heart. "Let's act on the suggestion. We can try our scheme later!"

Harry's hand had already found the levers. In a moment the ballast tanks were being filled with water. Gradually the vessel sank.

As the light grew more dim at the increased depth, Jimmie declared he could see the other vessel descending at about the same speed.

Presently the two craft were at the limit of their travel. The visitor rested on the deck of the Wanderer, while the 'U-13', in which the boys were imprisoned, hung again at an angle from the line.

Directly the lads saw the figure that had formerly attracted their attention. It was climbing the main shrouds of the wrecked ship. When the man reached a position level with their craft he began making signs and motions. In his hand he flourished a knife.

"Looks rather bad for us!" commented Jack.

"Don't you get him?" asked Jimmie impatiently. "He understands our predicament and intends to help us! He motioned out that he is going to climb the rigging until he can find the rope. Then he'll slide down it until he lands on our stern. If we'll agree not to start the engines while he's there, he'll cut the rope. But we must be ready at the ballast tanks to let the vessel settle slowly to the deck of the ship, so he can get off and clear the line from the propeller!"

"I don't believe it!" stated Jack. "I think he meant to cut the line as soon as he gets to it and let us settle down slowly. What would be the sense of his riding around the ocean seated on the stern of a disabled submarine? He's got too much sense for that!"

"Maybe you're right!" admitted Jimmie. "Let's float the boat on an even keel and see. I'm going to dress again!"

Even as the lad hastened to put on his clothes the boys felt a sudden dip made by the submarine. Gradually they descended.

"Hurrah, he did it!" exultantly cried Ned. "Now, where has he gone? I do hope he'll free the propeller wheel at once!"

"We could rise to the surface even if the propeller is stuck!" declared Harry. "I can pump the ballast all out of the tanks!"

"But if we do that we'll have to dive overboard to clear the wheel!" protested Frank. "I know that water is good and cold!"

"Wait a minute, boys, and see what the fellow does," cautioned Ned. "Maybe he wants to help us, so it wouldn't be nice to run away!"

"Here he is, now!" cried Jack from his position near a porthole. "He's looking through the glass, and making motions again!"

"I know what he wants!" declared Harry. "He's making motions for us to unscrew a pipe! He wants us to let in a lot of the ocean!"

"Wait a minute, Harry!" put in Ned. "He's walking toward his own boat. Let's see what he's going to do!"

In a short time their rescuer had reached the side of his own vessel. He stepped into an open door in the side and disappeared.

"An air lock!" cried Ned. "Did you see that, boys?"

"Just like the little old Sea Lion we used in the China Sea!"

"Here he comes again with a line!" announced Harry. "Now what?"

The boys heard a hammering and thumping near one of the sea cocks.



CHAPTER XIX

MACKINDER AGAIN

Even as the five boys glanced at each other with startled and wondering looks, the thumping ceased abruptly. In a short space it was resumed. Instinctively the boys gathered near the spot.

While they stood there trying to determine the cause for the strange procedure, the noise ceased. They heard a tapping at one of the portholes. Jimmie rushed across the compartment to investigate.

"Hey, fellows, come over here a minute!" he called out.

"What have you found now?" questioned Ned, obeying the request.

"Here's this chap, and he's making all sorts of signals!"

"That's funny!" puzzled Ned. "Can you make out what he wants?"

"He's making his hands go in the strangest way! I'm sure I can't interpret such motions unless he wants us to turn around while he places a bomb or something close enough to blow us out of the water."

"I know what he wants!" shouted Harry, who had been closely observing the stranger's repetition of the strange motions. "He wants us to open the valve leading from that sea cock where he has been working!"

"Fine business!" scorned Jimmie. "Open up the sea cock and let the ocean come running all over our nice carpets! I guess not!"

"I'm going to try it, anyway!" declared Harry. "If a little water does come in, the pumps will take care of it before it becomes dangerous. At least, it's well worth trying!"

"Go ahead, then, but don't blame me if anything happens!"

Harry moved to the vicinity of the spot where the stranger had been occupied but a few moments before. Jimmie was at the porthole.

A turn of the valve resulted in a sudden short inrush of water.

This ceased abruptly, bringing forth an exultant cry from Harry, while the other boys crowded around, speculating on the cause.

"I've got it!" cried Harry, dancing about the compartment. "I know what he's going to do. Go to the porthole, Jimmie, and see where our friend is now. Tell me just what he's doing. I'm going to stand guard over this valve here for a while in case something happens."

"He's going back into his little cage!" stated Jimmie from his position. "He's just shutting the outer door."

"Stand by to see something happen now, boys!" announced Harry.

"What's going to happen, Harry?" asked Jack.

Before Harry could answer, a sputter of water and air was observed at the open valve. A small quantity of water was blown out of the pipe. Following this came a rush of sweet, pure air that was very grateful to the boys after they had been using the vitiated atmosphere of their craft.

In fact, the lads were much nearer the complete exhaustion of their supply of usable atmosphere than they really comprehended.

"Um-m-m!" exclaimed Jimmie, inhaling great draughts of the incoming current. "Smell that, will you? It's just like a posy bed!"

"That's quite remarkable!" declared Ned, as he, too, sniffed the new atmosphere. "It does really seem to carry the odor of flowers!"

"Maybe it's a sort of gas that he's unloading on us to render us unconscious, so he can capture the whole outfit!" conjectured Jack.

"I don't believe it!" protested Ned. "I'm quite convinced that this is pure air. He seems to have quite a lot of it stored up!"

"Let's pump out some of this foul air and change with the new!"

"Go ahead!" consented Ned. "It's a good move, I'm sure!"

In a short time the boys began to feel the effects of the inflow of vitalized atmosphere. They were livelier, with less depression.

Directly their attention was attracted to the porthole again by a tapping. The stranger was once more trying to convey some information by signs. He repeated the motions of a short time before.

"I got you!" cried Harry, holding up a hand as a sign of understanding. "He wants us to shut the valve off. Perhaps he's given us all the nice fresh air that he feels it possible to spare!"

"Shut the valve, then," directed Ned.

"What's next?" spoke up Jimmie, listening to a slight hammering outside of the hull. "He's disconnecting the pipe now!"

"Better wait a bit and see what he wants us to do," cautioned Ned. "Maybe he's going to cut the line out of our propeller."

The lad's prediction was correct. In a very few moments they could hear the stranger working away at the encumbering line which held their propeller in a vise-like grip.

Not many minutes passed before the stranger again appeared at the porthole. Making a few signals easily comprehended by all, he repaired to his own craft, entering and closing the door of the air lock.

Almost immediately the other craft began to ascend perpendicularly.

"Guess we may as well make a mooch!" stated Jimmie, as he watched the other submarine rise out of their range of vision. "We're done here!"

"All right, let's get going!" agreed Harry, stepping toward the levers and preparing to start the motors at the pilot's command.

At once Jimmie sprang to the wheel. He gave a pull at the bell cord, jangling out a "go ahead" signal to Harry. As the latter touched the levers a startling crash at the stern of the craft was heard.

The motors spun the shaft around futilely without making headway.

With blanched faces the lads glanced about the craft. Harry's hand instinctively sought the levers again to turn off the current.

"What's the matter?" called Jimmie from his position.

"I don't know!" declared Harry. "It sounded as if that fellow had tied a can to us and we'd set it going! What did he do?"

"Let's pump the ballast out and rise straight to the surface," suggested Ned. "I noticed that he did that. Maybe there's a reason!"

Harry lost no time in acting on this suggestion. The electric pumps were not long in emptying the ballast tanks. With this weight removed, the boat quickly shot upward to the surface.

As the conning tower portholes rose above the surface, the boys noticed that the afternoon was far spent. Darkness already was gathering.

Ned was working frantically at the clamps securing the hatch cover. With a cry of delight he swung the cover out of position, admitting a cool breeze. The wind had died down, leaving the surface of the ocean comparatively smooth. Sufficient breeze was moving, however, to serve the purpose of airing out the interior of the craft without putting the great fans into commission. All the boys came to the tiny deck.

Lying but a few fathoms from their port side they discerned the other submarine. Clearly distinguishable on the sides were the great letters "U-13" painted in almost exact duplicate of those on their own boat.

"What do you know about that?" was Jimmie's surprised exclamation. "If that fellow isn't a dead ringer for this ship, I'm a Dutchman!"

"He surely does look a whole lot like us!" agreed Ned.

"I say, Frank," put in Harry eagerly, "is that the fellow that sank the ship you were on? Can you identify it now?"

Frank shook his head hesitatingly before he answered slowly: "Boys, I hate to say it, but it looks as like the other as two peas. I would not like to make an affidavit, but I'm willing to say that it bears a most remarkable resemblance to that other one, if it is 'other'!"

"Then, I guess we're done for!" despaired Jack. "If that's a German craft, we may as well hoist the white flag now and surrender!"

"Think they'll take us back to Germany?" asked Ned quizzically.

"I'm sure of it!" declared the boy. "And we won't stand much show, either, when they find that we've stolen this ship away from Helgoland!"

"Goodness!" exclaimed Ned suddenly. "I declare I'd actually forgotten that we were on board a stolen submarine. That does make it look rather dubious for us. We are in a pretty mess!" he added.

"Here comes someone now!" announced Jimmie. "Watch the hatch!"

A movement of the hatch cover on the other vessel indicated that someone was about to appear on deck. Slowly a figure stepped forth.

The stranger was of medium build, and wore a suit of blue with a round hat to match. He was carefully dressed. After taking a long survey of the group on the deck of the false "U-13," he waved a hand in welcome.

"He wants us to come over and pay him a visit!" stated Jimmie.

"Why don't you accept, then?" inquired Ned. "We're into it now and may as well be sociable. Being balky won't help matters any!"

"I would if we had a boat," announced the other.

"Maybe the real 'U-13' there has a boat they'd spare," suggested Jack. "Why don't you hail and ask him if he won't send a boat?"

"Hail him yourself if you want to! Maybe he don't talk English!"

"Try him on United States then!" laughed Jack. "I would!"

"Help yourself!" said Jimmie, leaning back against the rail.

"Ahoy the submarine!" shouted Jack in response to this suggestion. "We haven't a boat or we'd come over. Can you send a boat to us?"

Waving an arm as if comprehending the lad's statement and inquiry the figure on the other vessel clambered quickly to the after deck. After a moment's fumbling at what appeared to be a lock, he lifted a cover. In a short time the boys saw him drag from its place a small, light, steel boat.

This was at once launched over the side. Running out upon a light iron ladder the man dropped into the rowboat. He sculled the small craft quickly over the intervening distance and was soon alongside.

"Come aboard, sir," invited Ned, reaching out a hand to assist.

"Good night!" ejaculated Jimmie. "How did you ever get here so quickly, Mackinder? We thought you were aboard that warship!"

"I've been here a long time!" laughed the other, looking at the lad.

"You've made a quick trip, all right!" returned Jimmie.

The others crowded forward with eager, questioning looks. Upon the face of each was to be seen amazement, wonder and perplexity.

"Come aboard, Mackinder," invited Ned. "We'd like to hear an explanation of the strange goings on hereabouts. Can you help us?"

"First, I'd like to hear your explanations," stated the newcomer. "But before you start your story, please tell me why you call me Mackinder."

"Isn't that your name?" asked Jimmie. "Tell us that!"

"Yes, that's my name, you know!" replied the stranger, smilingly. "But how did you happen to know it? I'm rather puzzled, you know!"

"Why, you told us yourself on the train running into Amsterdam!" stated Jimmie, with rising indignation. "Then we called you by that name while you were trying to delay our start. Also Captain von Kluck used that name when he referred to you. I guess it's your name all right!"

"I don't deny that!" stated the newcomer. "What puzzles me is how you chaps know it so quickly, don't you know."

"It don't make much difference how we know the name so quickly," went on Jimmie. "We'd know you anywhere we saw you. We'd especially recognize that hand with the scar! That's a dead giveaway!"

The newcomer glanced quickly at his right hand, which Jimmie had indicated. As he brought it up to view, the boys could see a jagged scar running clear across the back. They had seen such a scar before.

With an accusing finger pointing at the disfigurement, Jimmie snapped out in crisp accents that indicated plainly his excitement:

"That's the same hand that tied and gagged me in the warehouse in Amsterdam, and the same hand that I saw shoved into the window of the frontier hut to get the 'U-13' package. Deny it if you can!"

"I am not going to deny anything, you know!" returned the other coolly. "You seem so positive about it there's little use denying!"

"You bet there's no use denying anything like that!" declared Jimmie with some heat. "You can't deny that you tried to sic the German torpedo boat destroyer onto us, either. You can't deny that you sneaked away from this very submarine when I was painting the name on the bow. You'd better not try to deny that you showed us to the British gunboat a while ago and got them to fire at us. If you start denying anything," the boy went on, "I'm going to deny that I'm neutral!"

With a laugh the newcomer threw back his head in amused fashion.

"Have your own way about it, you know," he replied, "but I'm going to tell you one thing. I'm not Mackinder!"



CHAPTER XX

A MYSTERIOUS CRAFT

The surprise of the lads at this declaration of their visitor was profound. They stared at the stranger who bore such a striking resemblance to Mackinder and who had just declared that he was not that person. Speechless at the apparent untruth, they could only stare.

Seeing their looks of astonishment at his declaration, the man laughed loudly, apparently enjoying hugely the joke that the boys could not see. Supporting himself against the rail, he gave vent to peals of merriment at the expense of the five young lads.

"So you don't believe me, eh?" he inquired at length, controlling himself with an effort. "I can't blame you, don't you know!"

"Say, Mackinder, you ought to be in vaudeville!" declared Jimmie in reply. "For a lightning change artist, you're decidedly it!"

"Thank you!" acknowledged Mackinder, choosing to accept the boy's words as a compliment. "You're almost too kind, don't you know!"

"And then," the boy went on, "as a monologue artist, you'd certainly have them all backed off the boards. I know a place in New York where you could draw down your two fifty per without half trying!"

"An engagement, do you mean?" queried the man, with interest.

"Just that!" stated Jimmie. "And then, there's another place up the Hudson a ways where you ought to be making little ones out of big ones. They give a fellow a long engagement there and supply costumes!"

"All of which means that you're spoofing me a bit, don't you know!" returned their visitor without resentment. He was apparently enjoying the situation hugely, and meant to make the most of it.

Seeing that his words failed to arouse or draw out the other, Jimmie turned disgustedly away to lean over the rail.

Ned began to question their guest, but was interrupted by Jimmie, who announced that he saw a steamer's smoke on the horizon.

"This water is quite thickly sprinkled with vessels of all sorts," said the alleged Mackinder. "Perhaps we'd better get out, you know!"

"What do you make that vessel out to be?" asked Ned.

"It doesn't make any difference what it is," replied the other, "we shall be better off if they don't find us! We don't need them!"

"Very well," put in Jimmie, "then we'll get up steam on this wagon and slide along. I'm going to say this to you, though, that Mackinder or no Mackinder, we're very grateful for your help. If we get an opportunity to reciprocate, we'll be only too glad to do it!"

With this, the boy turned and offered his hand to the man. It was grasped with a hearty grip that conveyed a sense of friendliness.

"You can help me right now," was the response. "Come aboard my vessel and give me a hand on a little project I have under way."

"I don't think we'd better do that right now," stated Jimmie. "You see, we're neutral, and we don't want to take sides either way!"

"So am I neutral! I care nothing for this awful war except to see it stop. I shall do nothing for either side, so rest easy on that score. But your propellor is broken by having that line jammed in it. You cannot navigate your vessel, and would better come aboard mine!"

Doubting this statement, Jimmie clambered into the small boat and sculled toward the stern of the false "U-13". There he could look into the water to a depth sufficient to confirm the other's statement.

"It's no use, boys," he declared, returning to the conning tower. "The blades of the propellor are damaged beyond use. We might as well go!"

Securing a line to the bow of the false "U-13" the man proposed to tow it to a safe place where it could be anchored to await repairs. Two trips were necessary to transfer the boys to the craft which had been of such signal service in their hour of extreme need.

Led by their recent guest, who was now their host, the lads descended into the interior of the vessel. Here a strange sight met their gaze. In cages canaries were twittering gaily while all about the bulkheads had been fastened pots of plants, some of which were in bloom.

"Now I understand why the air you so kindly pumped into our vessel had the odor of flowers and growing things!" declared Ned as he turned to their host. "You have things fixed pretty cozy here!"

"Just a touch now and again to make it look home-like!" said the man. "I prefer the sight of a flower to that of a cold steel bulkhead. Besides, it's more healthful to have a few plants about."

Harry was lost in admiration of the machinery which he declared to be far superior to that of the vessel they had lately abandoned.

With a touch their strange host sent the craft forward at a good speed. He explained to the lads a gyroscope arrangement by which he controlled the steering gear that kept the vessel on any chosen course and at any desired depth after once being adjusted.

"And now, if you please, Mr. Mackinder," questioned Jimmie at length, "will you be so good as to tell us what your mission may be?"

"Certainly!" replied the other frankly. "I see the steamer is not following us so I will take plenty of time to give you details."

"Thanks!" drily responded the lad. "We'll appreciate it!"

With a laugh the man seated himself on a locker and motioned the lads to do likewise. They listened intently as he proceeded:

"You perhaps all realize that the possession of wealth is the desire of almost every human being. I am not different from the rest in that respect at least. Owing to some family trouble which I shall not at this time detail, I was not given the advantages that accrue ordinarily to heirs. I think you will understand what I mean?"

"You were left out in the cold when they passed the dough?" asked Jimmie with a knowing look. "Just shoved one side?"

"That's about it!" replied the man. "But I resolved to get some money, nevertheless. I had a fertile imagination, some education and a very small amount of money. I did not want to take so cheap a way as to rob or cheat my fellow men. I was not shrewd enough to enter the business world. Therefore, I turned my attention to lost or buried treasure."

Jimmie delivered a broad wink toward Ned. It was not lost by their observant entertainer, who laughed much to the boy's confusion.

"Amongst other inventions that were in my brain was an instrument for detecting the presence of gold similar to the instrument called a compass. In this instance electricity had nothing to do with its action.

"To make a long story short, you know, I finally succeeded in perfecting the arrangement. It was an amusing circumstance that I had a very hard struggle preserving my last gold piece with which to test the device," he went on with a laugh at the recollection of his trials.

"At last, I thought I had my instrument perfected. I next needed only something on which to practice. With my precious treasure carefully guarded I succeeded in reaching the Gulf of Mexico, where it is said so much pirate gold has been buried. Wonderful to relate, I actually located and recovered a small amount. It was not large but helped me to fit out a vessel in which to make other cruises."

"And it really worked?" inquired Jimmie in a tone of unbelief.

"How well I shall presently demonstrate, you know," was the reply. "But I found that the crew was tricky. They helped me get a treasure aboard then calmly turned pirates themselves and ran away with the treasure. For nearly a year I had hard luck. Then I succeeded in locating a large sum of gold that had been buried by a man's grandfather.

"My past experiences had taught me that I could not trust anyone. Therefore I determined to prosecute my search in other channels.

"Piece by piece in different shops I had this vessel constructed after my own designs. The pieces were assembled in a part of the Gulf of Mexico little frequented. There I tried out the undersea boat, named it the 'U-13'—the 'U' standing for Undersea and the '13' in defiance of the popular superstition. But I found a new difficulty.

"The instrument, although working perfectly on land, was not reliable under the ocean, for as you know there is a large amount of suspended gold in sea water. That made the instrument unreliable."

"What did you want to go under water for, anyway?" asked Ned.

"Gold!" was the curt reply. "So I had to construct another device that would neutralize the local attraction of the sea water just on the same principle that the mariner has the two iron balls near his compass to overcome the local attraction on his vessel.

"Then I was prepared to pursue my quest for treasure undisturbed. My first venture was the recovery of a large sum from a sunken ship in Havana harbor. This provided me sufficient funds so that I put stores aboard and came across to seek for the vessels of the Spanish Armada."

"How did you get across the Atlantic?" asked Jimmie incredulously.

"In this vessel!" was the reply. "And most of the way under water, too, you know! I didn't want anyone to see me!"

"But you had to come up once in a while to get air!"

"Oh, no! Here is a contrivance," indicating a huge box-like affair, "with which I separate the oxygen from the hydrogen by electricity. Water, as you know, is composed of two gases—oxygen and hydrogen. Two atoms of hydrogen combined with one atom of oxygen and make a tiny bit of water. By the aid of this special device I segregate the two gases, use the oxygen and discharge the hydrogen overboard."

"I'm going to take my hat off to you!" declared Jimmie. "But you had to have some means to prevent discomfort from the storage batteries!"

"Not with these!" smiled the other. "I'm using, without permission, of course, a new storage battery that does away with the lead-sulphuric acid type of battery. The inventor is a man whose name is familiar to you all. He uses a nickel, iron oxide and steel combination in a solution of potash. This battery, instead of causing inflammation or even proving deadly as is the case with the old type, is actually a benefit to a person. It is exactly opposite in its effect to the old style."

"And you manage to make a cruise of days and days under water?"

"Surely!" smiled their host. "There's nothing to prevent it!"

"That's going some!" declared Jimmie. "But I don't believe you managed to dig up a lot of gold from the bottom of the ocean!"

"What is there to hinder?" questioned the other.

"Everything!" declared Jimmie. "In the first place there is all the water about. Then, too, it would be easier to take this instrument into the regions where gold is usually discovered on land. You could prospect with it in almost the positive knowledge that you would locate a vein. Digging then would be easy."

"Yes, but I don't like to dig!" laughed the other. "Perhaps I'm too lazy to do that sort of thing!"

"There's something queer here that I don't quite get," stated Jimmie. "Can't you explain a little more in detail?"

"Why, certainly, I'll be glad to elucidate!" was the answer. "You have in mind the securing of free gold in nuggets and dust. I go about it in quite another way. My purpose is to recover the minted coins that have been placed aboard ships. When the ships sink, no diver yet has been able to reach those in deep water. Therefore, most of the gold that has been carried to the bottom in sunken vessels is forever lost. I intend to recover a great deal of it!"

"Then when you know approximately where the vessel was wrecked or sunk," put in Ned, "you go to that neighborhood. Your instrument indicates the presence of gold and you follow its directions until the exact spot is reached. Then you step out and carry the money aboard your own craft. Is that the correct explanation?"

"You have it exactly. And I have done pretty well so far!"

"I don't believe it!" declared Jimmie flatly. "The whole thing sounds mighty fishy—not meaning any disrespect," he added addressing the man who sat leaning back against a bulkhead.

"But I assure you that what I have said is absolutely true!"

"I'm from Missouri!" stated Jimmie in a tone of doubt.

Their host stepped to a locker which he opened.

"Great Frozen Hot Boxes!" cried Jimmie.



CHAPTER XXI

A MYSTERY EXPLAINED

"Why, boys, look at this!" cried Jimmie, his voice rising to a shriek then trailing off into a whisper. "Did you ever see the like?"

"Let's see!" put in Frank, crowding forward. "What is it?"

Eagerly the boys gathered around the open compartment. They heard distinctly the tinkle of coins as Jimmie seized a handful and let them slip one by one back into place. Again and again the boy dived his hands into the yellow mass of metal. He raised handfuls of coin to look at them a moment, then let them drop from his grasp.

"Good Night!" he ejaculated at length, turning a round-eyed face to the man who stood smiling beside the group. "Why, you must have enough here to buy a farm and build a fence clear around it!"

"Quite likely I have!" declared the other quietly. "But there are two or three other wrecked vessels that I wish to visit before I stop. I have the exact locations charted and have examined the interiors."

"Why didn't you take the gold away with you, then?"

"For the very simple reason that I found one pair of hands not enough to perform the task. I could have taken the gold away from the sunken wrecks, but the matter of getting it ashore was another thing!"

"Why, what's to prevent?" asked Ned wonderingly.

"Several things!" declared the other. "In the first place the peculiar phase of human nature that makes every man mad when he sees a lot of money would operate against my plan of taking the gold ashore. Who could I hire to move the heavy stuff with any assurance of their honesty if they once found out what might be in the packages?"

"That's so!" admitted Ned thoughtfully. "Human nature is crooked!"

"My plan has been to find some one who needs the money and who would work on a percentage basis—share and share alike. We can then get the money ashore, negotiate the older coins that possess more than their face value, bank the current coins and be prepared to use the wealth exactly as we see fit. So long as it remains under water it is safe."

"But I can't understand how you get it aboard!" declared Jimmie.

"I have a tank of compressed air fixed to the back of a special diving suit," explained the man. "There's also a search light and a small storage battery provided. In this suit I step out through the air lock onto the wreck. The rest is easy. I return with the load of gold the same way I went out. The submarine is anchored. The whole thing is simple!"

"Sure enough!" exclaimed Jimmie. "Why didn't I remember our arrangement on the Sea Lion? And then, too, we saw you walking about on the decks of the Wanderer! I guess I'm going daffy!"

"What do you say, boys, will you join the expedition?"

"We don't stand much chance of getting home right away," stated Ned. "I guess we might as well—" what he would say was cut short by the sound of a cannon shot booming through the gathering darkness.

"What's that?" inquired Jack anxiously, jumping to his feet.

"I'll bet it's that bloomin' steamer we saw!" cried Jimmie. "That must be another of those gun boats and they're chasing us!"

"I'll go up to the deck and see!" offered Ned.

"Be careful, don't let them get you!" warned Jack.

"I'll watch out for that," laughed Ned, mounting the iron ladder.

Directly the little group at the foot of the ladder were startled to hear their companion's voice. A note of anxiety vibrated through his words.

"Boys," Ned cried, "there's a gunboat out there, and I think I see another submarine. It looks to be like the 'U-13' for all the world. What shall we do?"

"Here," urged Jimmie, "take the glasses and have a good look. If it is that Dutchman, I'm for beating it out of here mighty quick!"

For a tense moment Ned gazed through the glasses at the strange vessels. At length he lowered the binoculars and turned toward his companions. With a shake of his head and a quick indrawing of breath, he said:

"It's the 'U-13' as sure as can be!"

"Let's go!" was Jimmie's only comment as he turned toward the switchboard with outstretched hand.

"I'm with you!" declared Ned, quickly descending the ladder to join the group. "Go ahead slow, though. Don't break the hawser, or we'd lose the other vessel."

"Perhaps we would do better to abandon your vessel," Mackinder suggested as he prepared to go on deck. "Let me have the glasses, if you please. I'll look them over."

Jimmie paused, with his hand on the starting switch.

Suddenly all were startled by a cry from their host.

"Go ahead! go ahead!" he shouted down the hatchway. "That other fellow has launched a torpedo at us!"

"Let go the line, then!" urged Ned. "We'll have to run for it! Full speed, Jimmie!" he added.

Mackinder was casting off the hawser with rapid motions. Jimmie, in response to Ned's command, threw the switch over. The "U-13" began to gather headway.

All were startled to hear the report of a cannon shot. This was followed almost instantly by a shriek from the man on deck.

"Mackinder's hit!" gasped Ned, turning a blanched face to his chums. "What shall we do?"

As if in answer to his query, the voice of Mackinder reached the ears of the lads.

"Bring an axe!" he shouted. "I'm fast in the bight!"

Wrenching an axe from its pocket on the bulkhead, Ned sprang up the ladder at his best speed. On deck he found Mackinder caught in a bight of the hawser by which the other vessel had been towed. His leg was jammed against the fairleader. Only one glance was required to show the boy that serious injury had been done.

Without waiting for words, the lad stepped to the side of the fallen man. Swinging his axe quickly, he struck at the taut bond of hemp. A shower of sparks followed the ringing thud of the axe upon the steel deck.

Mackinder dropped back upon the deck, limp and helpless, as the singing of the parted line told of his release.

With tender solicitude the boys mounted the ladder to assist their injured friend to the room below. Scarcely had the boys gained the deck when they were startled by a terrific explosion. As Ned afterward declared, it seemed as if they had been caught in a volcano of water.

"What has happened?" queried Jack, releasing his hold upon Mackinder.

A flood of sea water descending upon the little deck prevented an answer to his question. In a moment the lads were able to look about.

"Where's our 'U-13'?" asked Harry.

"Gone!" stated Ned, his voice trembling. "I'll bet that German torpedoed it! I'm glad we are on this 'U-13'!"

Echoing this sentiment, the lads hastily proceeded to lower Mackinder through the hatchway. This done, the injured man was deposited on a couch, the hatch was closed, and Ned began first-aid ministrations.

"What course shall I hold?" asked Jimmie.

"Better head on a southwest course," stated Ned, briefly glancing up from his work over Mackinder's leg.

"I can do that all right," responded Jimmie. "The gunboat and the submarine can fight it out alone."

"We've got a clear field, Jimmie, so shove the little wagon along for all she's worth," put in Jack.

Mackinder had been exercising wonderful command of himself, but in spite of his best efforts a groan now and again escaped. The injured leg was proving a painful matter.

"We'll do all we can for you, Mackinder," Ned offered, "but we need better skill than is available here. Would it not be best to make at once for some port where we can secure the services of a surgeon?"

Mackinder's only reply was a nod. His teeth were closed tightly to suppress the cry of anguish from his hurt.

"Keep on the surface, boys," urged Ned as he went about making the man comfortable with such simple means as were at hand. "I believe we are not far from the coast."

Surrendering the wheel to Frank, and with Jack at the engines, Jimmie insisted upon mounting to the deck again to look about them.

Cool and sweet the air gushed down the little open hatchway upon the injured man. Under its influence and aided by the ministrations of Ned, the proprietor of the third "U-13" rapidly gained control of himself.

"Head west southwest," he instructed Ned. "We'll be mighty apt to find the mouth of the Thames on that course. There are many places I'd rather go, but you are right—we must have a surgeon!"

Giving the course to Harry, Ned proceeded to do everything in his power to ease the hurt of their friend.

"On deck, there!" announced Jimmie presently, his face at the hatchway.

"Hello!" answered Ned. "What is it?"

"I see a light about a point off the port bow!"

"What do you make it out to be?"

"I think it is a lighthouse!" declared Jimmie.

"Margate!" murmured Mackinder. "We are safe enough now, but be careful about the money, boys!"

"Sail ho!" rang out Jimmie's voice again.



CHAPTER XXII

MORE MYSTERY

"What do you see now, Jimmie?" asked Ned anxiously, stepping to the foot of the ladder.

"There's a small steamer coming up rapidly from the starboard side," replied the lookout.

"Perhaps we'd better dive again," suggested Ned.

"Aw, go on!" protested Jimmie. "What's the use of diving every time anything comes along? We're neutral!"

"We are, yes," agreed Ned, "but this 'U-13' name is not neutral, and if the steamer is an English vessel they'll probably not stop to ask questions."

"Why not swing a white light at 'em, then?"

"That's a good idea, too!" agreed Ned. "If they seem to be heading toward us, just get a white flag going."

"They are not showing any light at all," announced Jimmie. "They're just sneaking along like an express train."

"Let us know at once if anything happens," Ned responded, turning back to his patient.

The boys had not long to wait.

Out of the gathering darkness Jimmie saw a burst of flame which lighted up a portion of the approaching steamer. A bright flash in a wave some distance in advance of the "U-13" next attracted his attention. The sharp roar of a cannon came to the ears of all.

"Are they shooting at us?" asked Ned, again approaching the ladder.

"Don't know!" Jimmie replied briefly. "I saw the flash and heard the noise. There was a splash some distance ahead of us in the water. Maybe they can't aim straight."

Ned mounted the rungs of the ladder without further delay. He closed his eyes as he did so, the better to accommodate his vision to the change from the light below to the darkness outside. In a moment he was peering in the direction indicated by Jimmie.

"Can you make her out?"

"Yes," replied Ned. "I can just see a sort of thick place in the darkness. My eyes will be all right soon."

"I don't believe they were shooting at us at all!" commented Jimmie, musingly. "They can't see us!"

As if to disprove this statement, another flash lighted up the forward portion of the other vessel.

Ned grasped Jimmie's arm and pointed straight ahead.

Skipping from wave to wave, throwing up a fountain of spray from each, the shot from the steamer plowed its way across the path of the "U-13," passing so close that the boys were struck by the flying drops of water.

"That means that we are to stop!" declared Ned. "Next time they'll shoot at us!"

"And hit us, too!" excitedly put in the other.

Without waiting for orders from Ned, the lad leaned over the coaming of the little hatch.

"Shut her off, Jack!" he cried. "Back on your engines. That guy thinks we are Germans!"

Jack at once complied with the request, and soon the "U-13" was gently rolling in the trough of the sea.

Frank sprang from the wheel to the ladder, mounting to the deck just as a beam of flame from a powerful searchlight aboard the steamer swept the "U-13" from end to end.

In the glare of the light the three boys stood plainly visible. They could not, however, distinguish the details of the other vessel because of the flaming eye regarding them with unwinking stare.

For a few moments they stood close to each other, uncertain what to do. At length a voice hailed them.

"Submarine, ahoy! What vessel is that?"

"Shall I tell them our name?" asked Ned anxiously.

"No," urged Jimmie. "Don't say 'U-13'!"

"They've seen it on the side, anyhow!" scorned Frank.

"Don't let them think we're Germans. Don't you see they're English?" queried Jimmie.

"It doesn't signify they're English, even if they do speak the language," returned Ned. "Can't you answer?"

"Ahoy, there!" came an impatient voice.

"Steamer, ahoy!" replied Ned. "We're a peaceful submarine manned by neutral noncombatants!"

"A likely yarn, indeed!" laughed the stranger. "Stand by to receive a boat. I shall send an officer aboard to investigate."

"All right, Captain," consented Ned. "Glad to meet you!"

Still standing under the unwinking eye of the searchlight, the little group waited expectantly for the arrival of the boarding party.

A splash of oars preceded the boat which soon shot out of the darkness.

In another moment an officer in uniform had mounted the little deck. Wonderingly he glanced about the group, now augmented by the arrival of Jack and Harry.

"Where is your commander?" he inquired somewhat stiffly, addressing no one in particular.

Indicating Ned, the boys silently waited.

"Are you in charge of this vessel?" asked the officer, with just a trace of amusement.

"I am and I am not," replied Ned, with dignity.

"That's very enlightening, I'm sure," returned the other. "But time is short, and I must see the person who is in charge, and that at once."

"The owner is lying in the cabin with a broken leg which he received as we were escaping from a German submarine," explained Ned. "We boys are trying to get to some port where we can secure the services of a surgeon."

"Oh," exclaimed the officer, "escaping from a German?"

"Yes, sir. They torpedoed another submarine that we were towing, and in casting off the towing line the gentleman below was caught in the line. His leg is badly broken."

"Who is this other person?"

"He gave us the name of Mackinder."

A frown settled over the face of their questioner. Stepping forward, with flashing eyes he addressed Ned in a low voice vibrant with emotion.

"Now, if you have all the lies out of your system," he gritted, "we'll listen to the real story."

"That is the real story!" protested Ned. "Step below, if you don't believe me, and you may see for yourself."

"We have already seen enough to discredit such a wild yarn as that!" declared the other. "Too many of our brave sailors have been killed and set adrift by the 'U-13.' Besides, the man you mention is certainly not in the cabin. I can swear to that. Now, will you tell me the truth?"

"I say, Mister," put in Jimmie, "suppose you go fifty-fifty with us. Who are you, and what right have you to stop us?"

A short laugh was the man's only answer. He turned to hail the vessel from which he had just come.



CHAPTER XXIII

THE MYSTERY OF THE "U-13"

"Ahoy!" his hail rang out over the waters. "Send another boat aboard us. I will transfer the crew of this vessel!"

"Yes, you will!" scornfully replied Jimmie. "You'll do a lot, you will. We have something to say about that!"

"I am more astonished than I can say," the officer replied as he gazed at the lad. "I had supposed that Boy Scouts would not under any circumstances lend themselves to a project of an unworthy character."

"Well, who has done all that?" bristled Jimmie, wrinkling a freckled nose at the man. "You're taking a lot for granted, I must say! Who are you, anyhow?"

"You'll find out quickly enough!" was the answer.

Turning at the sound of approaching oars, the officer quickly issued a few short commands.

In obedience to his orders, the boys were required to enter the small boat without even an opportunity of going below.

"Dodson," ordered the officer, "take a couple of men and search the vessel for others. We were informed there were but five, but they may have confederates."

Wonderingly the lads sat in the boat as they were rowed across the intervening distance to the steamer. Scarcely had they set foot on deck before a line was passed to the submarine and the vessel was under way, towing their recent habitation.

An orderly conducted the lads directly to the cabin, where they were greeted by an officer seated at the head of a table. He arose as they entered and extended a hand to each.

Motioning to seats, the officer again busied himself with some papers on the table. For some time the boys glanced expectantly at each other, waiting for the officer to open the anticipated conversation.

Impatiently the boys waited, listening to the regular throbbing of the steamer's propellers that told they were again under way.

At length the silence was broken by the arrival of an orderly. Saluting, he reported briefly to the officer. A nod dismissed him.

"Boys," began the officer in a kindly tone, "we find ourselves rather puzzled by some mysterious circumstances which we hope you can explain. Will you assist us?"

"I assume from the looks of things aboard that you are English," answered Ned. "Am I correct?"

"You are. This is a scout vessel doing patrol duty along the coast. In common with others, we have been on the sharp lookout for a submarine named 'U-13,' which has been doing considerable damage to our shipping. We capture it without difficulty, to find it manned by Boy Scouts instead of Germans, as we had expected. Can you explain that?"

"Yes!" laughed Ned. "That is easy. The boat you have captured is owned by a private individual named Mackinder, who has been amusing himself in a perfectly innocent pastime. He, like ourselves, is neutral, but unfortunately has gotten into rather compromising situations."

"Mackinder?" repeated the officer, wonderingly.

"Yes, sir," continued Ned. "He rescued us from our disabled submarine. He is now aboard his vessel with a broken leg."

"We had him brought aboard this vessel, and find that his leg is really broken," explained the officer. "But," he continued, "you have not quite explained your presence on a submarine."

"That is easy—" began Ned. He was interrupted by a sign from the officer.

"Just a moment," the other said. "We will have Mackinder in here, and perhaps he can explain a little of the mystery himself."

At a command from the man two orderlies approached. In a few moments the boys observed four sailors bearing a mattress upon which lay their late host.

At the same moment a group approached from the after part of the cabin. Glancing from one group to the other, the boys rose to their feet with exclamations of surprise.

"Well, Great Frozen Hot Boxes!" cried Jimmie. "How did you get here, Mackinder?"

A man from the small group behind the officer stepped forward, smiling.

"I was picked up by the fishing boat you probably saw when I swam away from the submarine you captured. They transferred me to this craft. We have since been looking for you."

"Well, I'm glad to see you, anyway," returned the lad. "But you couldn't prevent our leaving Holland, even if you did try good and hard. Have you found that package yet?"

The smile quickly faded from the face of the other.

"No, I haven't," he answered in a low voice. "I find that you boys have gotten me into a lot of trouble, too."

"Trouble?" puzzled Ned. "How have we done that?"

"By secreting that package," explained Mackinder. "You see, I was detailed to duty on the Holland frontier. When I saw that package, and knew that you had recently come from the German lines, I assumed, of course, that it contained information for the German submarine that has been causing so much havoc amongst the English shipping. Without waiting for orders, I tried to follow you and gain possession of the object. Now it seems I am disobeying regulations by absenting myself from my post of duty without leave. Further, I was seen aboard or coming from a German vessel. Hence circumstances look bad for me. I'm due for a court martial as soon as we land at Margate, which must be close aboard by now."

All were startled to hear a groan escape the man lying upon the mattress. He had raised himself upon one elbow.

"Oh, Robert!" he cried. "Not that!"

"Tom!" gasped Mackinder. Soon the two men were shaking hands at a great rate, tears in their eyes.

"Boys," Mackinder announced at length, "I must introduce my brother Tom."

"We have had the pleasure of meeting the gentleman," stated Ned. "In fact, we owe our lives to his kindness."

"But, see here," demanded Jimmie, stepping forward, "this needs an explanation. Which one of you fellows was at the little cabin on the Holland border?"

Tom Mackinder smiled, in spite of the pain of his crushed leg. He turned his glance toward his brother, whose hand he held.

"We both were there, Jimmie," he said. "I took the package from the window. You see," he continued, "it contained plans of my submarine, with which you are familiar. I tried to sell the plans to Germany, but found they had beaten me. So upon my return trip I slipped the package into your baggage, thinking to escape search and detention at the border. I have it here now."

As he ceased speaking he drew from his pocket the same flat package the boys had seen before.

"Hurrah!" cried Jimmie. "Now we can explain how your brother came to be captured by the Germans, and how under his direction we stole the other 'U-13' and escaped from Helgoland."

"If what you say is true, young man," put in the officer, "the anticipated court martial may never convene."

"We can prove it!" protested Jimmie vigorously.

"Then we have solved the Mystery of the 'U-13'!" declared the officer, with evident relief.

"And now we'll head for the little old U. S. A. and peaceful neutrality!" was Jimmie's joyful comment.

"But you'll first arrange to care for your share of the cargo aboard my boat," interposed the injured Mackinder.

He would not entertain any of the objections raised by the boys, but insisted that they share in the treasure which had been recovered from the ocean's grasp.

A few days later as the boys watched the chalk cliffs of Dover slip away into the eastern horizon Jimmie turned from the rail of the steamer upon which they had taken passage.

"Good by, England, and good by the Mackinders," he said. "I'm glad we are out of the war zone at last and that we solved the Mystery of the 'U-13'."

THE END

* * * * *

The Aeroplane Series By John Luther Langworthy

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