X. The Submarine Mine
 

"Here's the bullet. What I want you to do, Professor Kennedy, is to catch the crank who fired it."

Capt. Lansing Marlowe, head of the new American Shipbuilding Trust, had summoned us in haste to the Belleclaire and had met us in his suite with his daughter Marjorie. Only a glance was needed to see that it was she, far more than her father, who was worried.

"You must catch him," she appealed. "Father's life is in danger. Oh, you simply must."

I knew Captain Marlowe to be a proverbial fire-eater, but in this case, at least, he was no alarmist. For, on the table, as he spoke, he laid a real bullet.

Marjorie Marlowe shuddered at the mere sight of it and glanced apprehensively at him as if to reassure herself. She was a tall, slender girl, scarcely out of her teens, whose face was one of those quite as striking for its character as its beauty. The death of her mother a few years before had placed on her much of the responsibility of the captain's household and with it a charm added to youth.

More under the spell of her plea than even Marlowe's vigorous urging, Kennedy, without a word, picked up the bullet and examined it. It was one of the modern spitzer type, quite short, conical in shape, tapering gradually, with the center of gravity back near the base.

"I suppose you know," went on the captain, eagerly, "that our company is getting ready to-morrow to launch the Usona, the largest liner that has ever been built on this side of the water-- the name is made up of the initials of the United States of North America.

"Just now," he added, enthusiastically, "is what I call the golden opportunity for American shipping. While England and Germany are crippled, it's our chance to put the American flag on the sea as it was in the old days, and we're going to do it. Why, the shipyards of my company are worked beyond their capacity now."

Somehow the captain's enthusiasm was contagious. I could see that his daughter felt it, that she was full of fire over the idea. But at the same time something vastly more personal weighed on her mind.

"But, father," she interrupted, anxiously, "tell them about the bullet."

The captain smiled indulgently as though he would say that he was a tough old bird to wing. It was only a mask to hide the fighting spirit underneath.

"We've had nothing but trouble ever since we laid the keel of that ship," he continued, pugnaciously, "strikes, a fire in the yard, delays, about everything that could happen. Lately we've noticed a motor-boat hanging about the river-front of the yards. So I've had a boat of my own patrolling the river."

"What sort of craft is this other?" inquired Kennedy, interested at once.

"A very fast one--like those express cruisers that we hear so much about now."

"Whose is it? Who was in it? Have you any idea?"

Marlowe shook his head doubtfully. "No idea. I don't know who owns the boat or who runs it. My men tell me they think they've seen a woman in it sometimes, though. I've been trying to figure it out. Why should it be hanging about? It can't be spying. There isn't any secrecy about the Usona. Why is it? It's a mystery."

"And the shot?" prompted Craig, tapping the bullet.

"Oh yes, let me tell you. Last night, Marjorie and I arrived from Bar Harbor on my yacht, for the launching. It's anchored off the yard now. Well, early this morning, while it was still gray and misty, I was up. I'll confess I'm worried over to-morrow. I hadn't been able to forget that cruiser. I was out on the deck, peering into the mist, when I'm sure I saw her. I was just giving a signal to the boat we have patrolling, when a shot whistled past me and the bullet buried itself in the woodwork of the main saloon back of me. I dug it out of the wood with my knife--so you see I got it almost unflattened. That's all I have got, too. The cruiser made a getaway, clean."

"I'm sure it was aimed at him," Marjorie exclaimed. "I don't think it was chance. Don't you see? They've tried everything else. Now if they could get my father, the head of the company, that would be a blow that would cripple the trust."

Marlowe patted his daughter's hand reassuringly and smiled again, as though not to magnify the incident.

"Marjorie was so alarmed," he confessed, "that nothing would satisfy her but that I should come ashore and stay here at the Belleclaire, where we always put up when we are in town."

The telephone rang and Marjorie answered it. "I hope you'll pardon me," she excused, hanging up the receiver. "They want me very much down-stairs." Then appealing, she added: "I'll have to leave you with father. But, please, you must catch that crank who is threatening him."

"I shall do my level best," promised Kennedy. "You may depend on that."

"You see," explained the captain as she left us, "I've invited quite a large party to attend the launching, for one reason or another. Marjorie must play hostess. They're mostly here at the hotel. Perhaps you saw some of them as you came in."

Craig was still scanning the bullet. "It looks almost as if some one had dum-dummed it," he remarked, finally. "It's curiously done, too. Just look at those grooves."

Both the captain and I looked. It had a hard jacket of cupro- nickel, like the army bullet, covering a core of softer metal. Some one had notched or scored the jacket as if with a sharp knife, though not completely through it. Had it been done for the purpose of inflicting a more frightful wound if it struck the captain?

"There've been other shots, too," went on Marlowe. "One of my watchmen was wounded the night before. It didn't took like a serious wound, in the leg. Yet the poor fellow seems to be in a bad way, they tell me."

"How is that?" asked Craig, glancing up quickly from studying the bullet.

"The wound seems to be all puffed up, and very painful. It won't heal, and he seems to be weak and feverish. Why, I'm afraid the man will die."

"I'd like to see that case," remarked Kennedy, thoughtfully.

"Very well. I'll have you driven to the hospital where we have had to take him."

"I'd like to see the yards, too, and the Usona," he added.

"All right. After you go to the hospital I'll meet you at the yards at noon. Now if you'll come down-stairs with me, I'll get my car and have you taken to the hospital first."

We followed Marlowe into the elevator and rode down. In the large parlor we saw that Marjorie Marlowe had joined a group of the guests, and the captain turned aside to introduce us.

Among them I noticed a striking-looking woman, somewhat older than Marjorie. She turned as we approached and greeted the captain cordially.

"I'm so glad there was nothing serious this morning," she remarked, extending her hand to him.

"Oh, nothing at all, nothing at all," he returned, holding the hand, I thought, just a bit longer than was necessary. Then he turned to us, "Miss Alma Hillman, let me present Professor Kennedy and Mr. Jameson."

I was not so preoccupied in taking in the group that I did not notice that the captain was more than ordinarily attentive to her. Nor can I say that I blamed him, for, although he might almost have been her father in age, there was a fascination about her that youth does not often possess.

Talking with her had been a young man, slender, good-looking, with almost a military bearing.

"Mr. Ogilvie Fitzhugh," introduced Marjorie, seeing that her father was neglecting his duties.

Fitzhugh bowed and shook hands, murmured something stereotyped, and turned again to speak to Marjorie.

I watched the young people closely. If Captain Marlowe was interested in Alma, it was more than evident that Fitzhugh was absolutely captivated by Marjorie, and I fancied that Marjorie was not averse to him, for he had a personality and a manner which were very pleasing.

As the conversation ran gaily on to the launching and the gathering party of notables who were expected that night and the next day, I noticed that a dark-eyed, dark-haired, olive- complexioned young man approached and joined us.

"Doctor Gavira," said Marlowe, turning to us, his tone indicating that he was well acquainted about the hotel. "He is our house physician."

Gavira also was welcomed in the party, chatting with animation. It was apparent that the physician also was very popular with the ladies, and it needed only half an eye to discern that Fitzhugh was jealous when he talked to Marjorie, while Marlowe but ill concealed his restlessness when Gavira spoke to Alma. As for Alma, she seemed to treat all men impartially, except that just now it pleased her to bestow the favor of her attention on the captain.

Just then a young lady, all in white, passed. Plainly she did not belong to the group, though she was much interested in it. As his eye roved over the parlor, Gavira caught her glance and bowed. She returned it, but her look did not linger. For a moment she glanced sharply at Fitzhugh, still talking to Marjorie, then at Marlowe and Alma Hillman. She was a very pretty girl with eyes that it was impossible to control. Perhaps there was somewhat of the flirt in her. It was not that that interested me. For there was something almost akin to jealousy in the look she gave the other woman. Marlowe was too engrossed to see her and she passed on slowly. What did it mean, if anything?

The conversation, as usual at such times, consisted mostly of witticisms, and just at present we had a rather serious bit of business in hand. Kennedy did not betray any of the impatience that I felt, yet I knew he was glad when Marlowe excused himself and we left the party and passed down the corridor while the captain called his car.

"I don't know how you are going to get at this thing," he remarked, pausing after he had sent a boy for his driver. "But I'll have to rely on you. I've told you all I know. I'll see you at noon, at the yards. My man will take you there."

As he turned and left us I saw that he was going in the direction of the barber-shop. Next to it and in connection with it, though in a separate room, was a manicure. As we passed we looked in. There, at the manicure's table, sat the girl who had gone by us in the parlor and had looked so sharply at Marlowe and Alma.

The boy had told us that the car was waiting at a side entrance, but Kennedy seemed now in no haste to go, the more so when Marlowe, instead of going into the barber-shop, apparently changed his mind and entered the manicure's. Craig stopped and watched. Prom where we were we could see Marlowe, though his back was turned, and neither he nor the manicure could see us.

For a moment the captain paused and spoke, then sat down. Quite evidently he had a keen eye for a pretty face and trim figure. Nor was there any mistaking the pains which the manicure took to please her rich and elderly customer. After watching them a moment Kennedy lounged over to the desk in the lobby.

"Who is the little manicure girl?" he asked.

The clerk smiled. "Seems as if she was a good drawing-card for the house, doesn't it?" he returned. "All the men notice her. Why, her name is Rae Melzer." He turned to speak to another guest before Kennedy could follow with another inquiry.

As we stood before the desk, a postman, with the parcel post, arrived. "Here's a package addressed to Dr. Fernando Gavira," he said, brusquely. "It was broken in the mail. See?"

Kennedy, waiting for the clerk to be free again, glanced casually at the package at first, then with a sudden, though concealed, interest. I followed his eye. In the crushed box could be seen some thin broken pieces of glass and a wadding of cotton-wool.

As the clerk signed for another package Craig saw a chance, reached over and abstracted two or three of the broken pieces of glass, then turned with his back to the postman and clerk and examined them.

One I saw at once had a rim around it. It was quite apparently the top of a test-tube. The other, to which some cotton-wool still adhered, was part of the rounded bowl. Quickly Craig dropped the pieces into one of the hotel envelopes that stood in a rack on the desk, then, changing his mind about asking more now about the little manicure, strode out of the side entrance where Marlowe's car was waiting for us.

Hurriedly we drove across town to the City Hospital, where we had no difficulty in being admitted and finding, in a ward, on a white cot, the wounded guard. Though his wound was one that should not have bothered him much, it had, as Marlowe said, puffed up angrily and in a most peculiar manner. He was in great pain with it and was plainly in a bad way.

Though he questioned the man, Craig did not get anything out of him except that the shot had come from a cruiser which had been hanging about and was much faster than the patrol boat. The nurse and a young intern seemed inclined to be reticent, as though we might imply that the mail's condition reflected on the care he had received, which they were at pains to convince us had been perfect.

Puzzled himself, Craig did not say much, but as he pondered the case, shook his head gravely to himself and finally walked out of the hospital abstractedly.

"We have almost an hour before we are to meet Marlowe at the yard," he considered, as we came to the car. "I think I'll go up to the laboratory first."

In the quiet of his own workshop, Kennedy carefully examined again the peculiar grooves on the bullet. He was about to scrape it, but paused. Instead, he filled a tube with a soapy solution, placed the bullet in it, and let it stand. Next he did the same with the pieces of glass from the envelope.

Then he opened a drawer and from a number of capillary pipettes selected a plain capillary tube of glass. He held it in the flame of a burner until it was red hot. Then carefully he drew out one end of the tube until it was hair fine. Again he heated the other end, but this time he let the end alone, except that he allowed it to bend by gravity, then cool. It now had a siphon curve. Another tube he treated in the same way.

By this time he was ready to proceed with what he had in mind. He took a glass slide and on it placed a drop from each of the tubes containing the bullet and the glass. That done, he placed the bent, larger end of the capillary tubes in turn on each of the drops on the slide. The liquid ascended the tubes by capillary attraction and siphoned over the curve, running as he turned the tubes up to the finely pointed ends.

Next in a watch glass he placed some caustic soda and in another some pyrogallic acid, from each of which he took just a drop, as he had done before, inclining the tubes to let the fluid gravitate to the throttle end. Finally in the flame he sealed both the tip and butt of the tubes.

"There's a bubble of air in there," he remarked. "The acid and the soda will absorb the oxygen from it. Then I can tell whether I'm right. By the way, we'll have to hurry if we're to be on time to meet Marlowe in the yard," he announced, glancing at his watch as he placed the tubes in his little electric incubator.

We were a little late as the chauffeur pulled in at the executive offices at the gate of the shipyard, and Marlowe was waiting impatiently for us. Evidently he wanted action, but Kennedy said nothing yet of what he suspected and appeared now to be interested only in the yard.

It was indeed something to interest any one. Everywhere were tokens of feverish activity, in office, shop, and slip. As we picked our way across, little narrow and big wide gauge engines and trains whistled and steamed about. We passed rolling-mills, forging-machines, and giant shearing-machines, furnaces for heating the frames or ribs, stone floors on which they could be pegged out and bent to shape, places for rolling and trimming the plates, everything needed from the keel plates to the deck.

In the towering superstructure of the building slip we at last came to the huge steel monster itself, the Usona. As we approached, above us rose her bow, higher than a house, with poppets both there and at the stern, as well as bracing to support her. All had been done up to the launching, the stem and stern posts set in place, her sides framed and plated up, decks laid, bulkheads and casings completed, even much of her internal fitting done.

Overhead and all about the huge monster was a fairy network of steel, the vast permanent construction of columns and overhead girders. Suspended beneath was a series of tracks carrying traveling and revolving cranes capable of handling the heaviest pieces. We climbed to the top and looked down at the vast stretch of hundreds of feet of deck. It was so vast that it seemed rather the work of a superman than of the puny little humans working on her.

As I looked down the slip where the Usona stood inclined about half an inch to the foot, I appreciated as never before what a task it was merely to get her into the water.

Below again, Marlowe explained to us how the launching ways were composed of the ground ways, fastened to the ground as the name implied, and the sliding ways that were to move over them. The sliding ways, he said, were composed of a lower course and an upper course, on which rested the "cradle," fitting closely the side of the ship.

To launch her, she must be lifted slightly by the sliding ways and cradle from the keel blocks and bilge blocks, and this was done by oak wedges, hundreds of which we could see jammed between the upper and lower courses of sliding ways. Next he pointed out the rib-bands which were to keep the sliding ways on the ground ways, and at the bow the points on either side where the sliding and ground ways were bolted together by two huge timbers known as sole pieces.

"You see," he concluded, "it is a gigantic task to lift thousands of tons of steel and literally carry it a quarter of a mile to forty feet of water in less than a minute. Everything has to be calculated to a nicety. It's a matter of mathematics--the moment of weight, the moment of buoyancy, and all that. This launching apparatus is strong, but compared to the weight it has to carry it is really delicate. Why, even a stray bolt in the ways would be a serious matter. That's why we have to have this eternal vigilance."

As he spoke with a significant look at Kennedy, I felt that it was no wonder that Marlowe was alarmed for the safety of the ship. Millions were at stake for just that minute of launching.

It was all very interesting and we talked with men whom it was a pleasure to see handling great problems so capably. But none could shed any light on the problem which it was Kennedy's to solve. And yet I felt sure, as I watched Craig, that unsatisfactory as it appeared to Marlowe and to myself, he was slowly forming some kind of theory, or at least plan of action, in his head.

"You'll find me either here or at the hotel--I imagine," returned Marlowe to Kennedy's inquiry as we parted from him. "I've instructed all the men to keep their eyes open. I hope some of us have something to report soon."

Whether or not the remark was intended as a hint to Kennedy, it was unnecessary. He was working as fast and as surely as he could, going over in hours what others had failed to fathom in weeks.

Late in the afternoon we got back to the laboratory and Craig began immediately by taking from the little electric incubator the two crooked tubes he had left there. Breaking off the ends with tweezers, he began examining on slides the two drops that exuded, using his most powerful microscope. I was forced to curb my impatience as he proceeded carefully, but I knew that Craig was making sure of his ground at each step.

"I suppose you're bursting with curiosity," he remarked at last, looking up from his examination of one of the slides. "Well, here is a drop that shows what was in the grooves of that bullet. Just take a look."

I applied my eye to the microscope. All I could see was some dots and rods, sometimes something that looked like chains of dots and rods, the rods straight with square ends, sometimes isolated, but more usually joined end to end in long strings.

"What is it?" I asked, not much enlightened by what he had permitted me to see. "Anaerobic bacilli and spores," he replied, excitedly. "The things that produce the well-known 'gas gangrene' of the trenches, the gas phlegmon bacilli--all sorts, the bacillus aerogenes capsulatus, bacillus proteus, pyogenic cocci, and others, actively gas-forming microbes that can't live in air. The method I took to develop and discover them was that of Col. Sir Almroth Wright of the British army medical corps."

"And that is what was on the bullet?" I queried.

"The spores or seeds," he replied. "In the tubes, by excluding the air, I have developed the bacilli. Why, Walter," he went on, seriously, "those are among the microbes most dreaded in the infection of wounds. The spores live in the earth, it has been discovered, especially in cultivated soil, and they are extraordinarily long-lived, lying dormant for years, waiting for a chance to develop. These rods you saw are only from five to fifteen thousandths of a millimeter long and not more than one- thousandth of a millimeter broad.

"You can't see them move here, because the air has paralyzed them. But these vibrios move among the corpuscles of the blood just as a snake moves through the grass, to quote Pasteur. If I colored them you would see that each is covered with fine vibrating hairs three or four times as long as itself. At certain times an oval mass forms in them. That is the spore which lives so long and is so hard to kill. It was the spores that were on the bullet. They resist any temperature except comparatively high and prolonged, and even resist antiseptics for a long time. On the surface of a wound they aren't so bad; but deep in they distil minute gas bubbles, puff up the surrounding tissues, and are almost impossible to combat."

As he explained what he had found, I could only stare at him while the diabolical nature of the attack impressed itself on my mind. Some one had tried to murder Marlowe in this most hideous way. No need to be an accurate marksman when a mere scratch from such a bullet meant ultimate death anyhow.

Why had it been done and where had the cultures come from? I asked myself. I realized fully the difficulty of trying to trace them. Any one could purchase germs, I knew. There was no law governing the sale.

Craig was at work again over his microscope. Again he looked up at me. "Here on this other film I find the same sort of wisp-like anaerobes," he announced. "There was the same thing on those pieces of glass that I got."

In my horror at the discovery, I had forgotten the broken package that had come to the hotel desk while we stood there.

"Then it was Gavira who was receiving spores and cultures of the anaerobes!" I exclaimed, excitedly.

"But that doesn't prove that it was he who used them," cautioned Craig, adding, "not yet, at least."

Important as the discoveries were which he had made, I was not much farther along in fixing the guilt of anybody in particular in the case. Kennedy, however, did not seem to be perturbed, though I wondered what theory he could have worked out.

"I think the best thing for us to do will be to run over to the Belleclaire," he decided as he doffed his laboratory coat and carefully cleansed his hands in an antiseptic almost boiling hot. "I should like to see Marlowe again, and, besides, there we can watch some of these people around him."

Whom he meant other than Gavira I had no idea, but I felt sure that with the launching now only a matter of hours something was bound to happen soon.

Marlowe was out when we arrived; in fact, had not yet returned from the yard. Nor had many of the guests remained at the hotel during the day. Most of them had been out sightseeing, though now they were returning, and as they began to gather in the hotel parlor Marjorie was again called on to put them at their ease.

Fitzhugh had returned and had wasted no time dressing and getting down-stairs again to be near Marjorie. Gavira also appeared, having been out on a case.

"I wish you would call up the shipyard, Walter," asked Kennedy, as we stood in the lobby, where we could see best what was going on. "Tell him I would like to see him very urgently."

I found the number and entered a booth, but, as often happens, the telephone central was overwhelmed by the rush of early-evening calls, and after waiting some time the only satisfaction I got was that the line was busy.

Meanwhile I decided to stick about the booth so that I could get the yard as soon as possible. From where I stood I could see that Kennedy was closely watching the little manicure, Rae Melzer. A moment later I saw Alma Hillman come out of the manicure shop, and before any one else could get in to monopolize the fascinating little manicure I saw Craig saunter over and enter.

I was so interested in what he was doing that for the moment I forgot about my call and found myself unconsciously moving over in that direction, too. As I looked in I saw that he was seated at the little white table, in much the same position as Marlowe had been, deeply in conversation with the girl, though of course I could not make out what they were talking about.

Once she turned to reach something on a shelf back of her. Quick as a flash Kennedy abstracted a couple of the nearest implements, one being a nail file and the other, I think, a brush. A moment later she resumed her work, Kennedy still talking and joking with her, though furtively observing.

"Where is my nail file--and brush?" I could imagine her saying, as she hunted for them in pretty confusion, aided by Kennedy who, when he wanted to, could act the Fitzhugh and Gavira as well as they. The implements were not to be found and from a drawer she took another set.

Just then Gavira passed on his way to his office in the front of the building, saw me, and smiled. "Kennedy's cut you out," he laughed, catching a glimpse through the door. "Never mind. I used to think I had some influence there myself--till the captain came along. I tell you these oldsters can give us points."

I laughed, too, and joined him down the hall, not because I cared what he thought, but because his presence had reminded me of my original mission to call up Marlowe. However, I decided to postpone calling another moment and take advantage of the chance to talk to the house physician.

"Yes," I agreed, as long as he had opened the subject. "I fancy the captain likes young people. He seems to enjoy being with them- -Miss Hillman, for instance."

Gavira shot a sidelong glance at me. "The Belleclaire's a dangerous place for a wealthy widower," he returned. "I had some hopes in that direction myself--in spite of Fitzhugh--but the captain seems to leave us all at the post. Still, I suppose I may still be a brother to her--and physician. So, I should worry."

The impression I got of Gavira was that he enjoyed his freedom too much ever to fall in love, though an intimacy now and then with a clever girl like Alma Hillman was a welcome diversion.

"I'm sorry I sha'n't be able to be with you until late to-night," he said, as he paused at his office door. "I'm in the medical corps of the Guard and I promised to lecture to-night on gunshot wounds. Some of my material got smashed up, but I have my lantern slides, anyhow. I'll try to see you all later, though."

Was that a clever attempt at confession and avoidance on his part? I wondered. But, then, I reflected he could not possibly know that we knew he had anaerobic microbes and spores in his possession. I had cleared up nothing and I hastened to call up the shipyard, sure that the line could not be busy still.

Whatever it was that was the matter, central seemed unable to get me my number. Instead, I found myself cut right into a conversation that did not concern me, evidently the fault of the hotel switchboard operator. I was about to protest when the words I heard stopped me in surprise. A man and a woman were talking, though I could not recognize the voices and no names were used.

"I tell you I won't be a party to that launching scheme," I heard the man's voice. "I wash my hands of it. I told you that all along."

"Then you're going to desert us?" came back the woman's voice, rather tartly. "It's for that girl. Well, you'll regret it. I'll turn the whole organization on you--I will--you--you--" The voices trailed off, and, try as I could to get the operator to find out who it was, I could not.

Who was it? What did it mean?

Kennedy had finished with the manicure some time before and was waiting for me impatiently.

"I haven't been able to get Marlowe," I hastened, "but I've had an earful." He listened keenly as I told him what I had heard, adding also the account of my encounter with Gavira.

"It's just as I thought--I'll wager," he muttered, excitedly, under his breath, taking a hurried turn down the corridor, his face deeply wrinkled.

"Well! Anything new? I expected to hear from you, but haven't," boomed the deep voice of Marlowe, who had just come in from an entrance in another direction from that which we were pacing. "No clue yet to my crank?"

Without a word, Kennedy drew Marlowe aside into a little deserted alcove. Marlowe followed, puzzled at the air of mystery.

Alone, Craig leaned over toward him. "It's no crank," he whispered, in a low tone. "Marlowe, I am convinced that there is a concerted effort to destroy your plans for American commerce building. There isn't the slightest doubt in my mind that it is more serious than you think--perhaps a powerful group of European steamship men opposed to you. It is economic war! You know they have threatened it at meetings reported in the press all along. Well, it's here!"

Half doubting, half convinced, Marlowe drew back. One after another he shot a rapid fire of questions. Who, then, was their agent who had fired the shot? Who was it who had deserted, as I had heard over the wire? Above all, what was it they had planned for the launching? The deeper he got the more the beads of perspiration came out on his sunburnt forehead. The launching was only eighteen hours off, too, and ten of them were darkness. What could be done?

Kennedy's mind was working rapidly in the crisis as Marlowe appealed to him, almost helplessly.

"May I have your car to-night?" asked Craig, pausing.

"Have it? I'll give it to you if it'll do any good."

"I'll need it only a few hours. I think I have a scheme that will work perfectly--if you are sure you can guard the inside of the yard to-morrow."

"I'm sure of that. We spent hours to-day selecting picked men for the launching, going over everything."

Late as it was to start out of town, Craig drove across the bridge and out on Long Island, never stopping until we came to a small lake, around the shores of which he skirted, at last pausing before a huge barn-like structure.

As the door swung open to his honking the horn, the light which streamed forth shone on a sign above, "Sprague Aviation School." Inside I could make out enough to be sure that it was an aeroplane hangar.

"Hello, Sprague!" called Kennedy, as a man appeared in the light.

The man came closer. "Why, hello, Kennedy! What brings you out here at such an hour?"

Craig had jumped from the car, and together the two went into the hangar, while I followed. They talked in low tones, but as nearly as I could make out Kennedy was hiring a hydro-aeroplane for to- morrow with as much nonchalance as if it had been a taxicab.

As Kennedy and his acquaintance, Sprague, came to terms, my eye fell on a peculiar gun set up in a corner. It had a tremendous cylinder about the barrel, as though it contained some device to cool it. It was not a machine-gun of the type I had seen, however, yet cartridges seemed to be fed to it from a disk on which they were arranged radially rather than from a band. Kennedy had risen to go and looked about at me.

"Oh, a Lewis gun!" he exclaimed, seeing what I was looking at. "That's an idea. Sprague, can you mount that on the plane?"

Sprague nodded. "That's what I have it here for," he returned. "I've been testing it. Why, do you want it?"

"Indeed I do! I'll be out here early in the morning, Sprague."

"I'll be ready for you, sir," promised the aviator.

Speeding back to the city, Kennedy laid out an extensive program for me to follow on the morrow. Together we arranged an elaborate series of signals, and that night, late as it was, Craig returned to the laboratory, where he continued his studies with the microscope, though what more he expected to discover I did not know.

In spite of his late hours, it was Craig who wakened me in the morning, already prepared to motor out to the aviation school to meet Sprague. Hastily he rehearsed our signals, which consisted mostly of dots and dashes in the Morse code which Craig was to convey with a flag and I to receive with the aid of a powerful glass.

I must admit that I felt somewhat lost when, later in the morning, I took my place alone on the platform that had been built for the favored few of the launching party at the bow of the huge Usona, without Craig. Already, however, he had communicated at least a part of his plan to Marlowe, and the captain and Marjorie were among the first to arrive. Marjorie never looked prettier in her life than she did now, on the day when she was to christen the great liner, nor, I imagine, had the captain ever been more proud of her.

They had scarcely greeted me when we heard a shout from the men down at the end of the slip that commanded a freer view of the river. We craned our necks and in a moment saw what it was. They had sighted the air-boat coming down the river.

I turned the glass on the mechanical bird as it soared closer. Already Kennedy had made us on the platform and had begun to signal as a test. At least a part of the suspense was over for me when I discovered that I could read what he sent.

So fixed had my attention been that I had not noticed that slowly the members of the elect launching party had arrived, while other thousands of the less favored crowded into the spaces set apart for them. On the stand now with us were Fitzhugh and Miss Hillman, while, between glances at Kennedy, I noticed little Rae Melzer over at the right, and Doctor Gavira, quite in his element, circulating about from one group to another.

Every one seemed to feel that thrill that comes with a launching, the appreciation that there is a maximum of risk in a minimum of time.

Down the slip the men were driving home the last of the huge oak wedges which lifted the great Usona from the blocks and transferred her weight to the launching ways as a new support. All along the stationary, or ground, ways and those which were to glide into the water with the cradle and the ship, trusted men were making the final examination to be as sure as human care can be that all was well.

As the clock neared noon, which was high water, approximately, all the preparatory work was done. Only the sole pieces before us held the ship in place. It was as though all bridges had been burned.

High overhead now floated the hydro-aeroplane, on which I kept my eye fixed almost hypnotically. There was still no signal from Kennedy, however. What was it he was after? Did he expect to see the fast express cruiser, lurking like a corsair about the islands of the river? If so, he gave no sign.

Men were quitting now the work of giving the last touches to the preparations. Some were placing immense jack-screws which were to give an initial impulse if it were needed to start the ship down the ways. Others were smearing the last heavy dabs of tallow, lard oil, and soft soap on the ways, and graphite where the ways stretched two hundred feet or so out into the water, for the ship was to travel some hundreds of feet on the land and in the water, and perhaps an equal distance out beyond the end of the ways.

Late comers still crowded in. Men now reported that everything was ready. Steadily the time of high water approached.

"Saw the sole pieces!" finally rang out the order.

That was a thing that must be done by two gangs, one on each side, and evenly, too. If one gang got ahead of the other, they must stop and let the second catch up.

"Zip--zip--zip," came the shrill singing tone of the saws.

Was everything all right? Kennedy and Sprague were still circling overhead, at various altitudes. I redoubled my attention at the glass.

Suddenly I saw Craig's flag waving frantically. A muffled exclamation came from my lips involuntarily. Marlowe, who had been watching me, leaned closer.

"What is it--for God's sake?" he whispered, hoarsely.

"Stop them!" I shouted as I caught Kennedy's signal. At a hurried order from Marlowe the gangs quit. A hush fell over the crowd.

Kennedy was circling down now until at last the air-boat rested on the water and skimmed along toward the ways.

Out on the ways, as far as they were not yet submerged, some men ran, as if to meet him, but Kennedy began signaling frantically again. Though I had not been expecting it, I made it out.

"He wants them to keep back," I called, and the word was passed down the length of the ship.

Instead of coming to rest before the slip, the plane turned and went away, making a complete circle, then coming to rest. To the surprise of every one, the rapid staccato bark of the Lewis gun broke the silence. Kennedy was evidently firing, but at what? There was nothing in sight.

Suddenly there came a tremendous detonation, which made even the launching-slip tremble, and a huge column of water, like a geyser, rose in the air about eight hundred feet out in the river, directly in front of us.

The truth flashed over us in an instant. There, ten feet or so in the dark water out in the river, Craig had seen a huge circular object, visible only against a sandy bottom from the hydro- aeroplane above, as the sun-rays were reflected through the water. It was a contact submarine mine.

Marlowe looked at me, his face almost pale. The moment the great hulk of the Usona in its wild flight to the sea would have hit that mine, tilting it, she would have sunk in a blast of flame.

The air-boat now headed for the shore, and a few moments later, as Craig climbed into our stand, Marlowe seized him in congratulation too deep for words.

"Is it all right?" sang out one of the men in the gangs, less impressionable than the rest.

"If there is still water enough," nodded Craig.

Again the order to saw away the sole pieces was given, and the gangs resumed. "Zip--zip," again went the two saws.

There were perhaps two inches more left, when the hull quivered. There was a crashing and rending as the timbers broke away.

Marjorie Marlowe, alert, swung the bottle of champagne in its silken net on a silken cord and it crashed on the bow as she cried, gleefully, "I christen thee Usona!"

Down the ship slid, with a slow, gliding motion at first, rapidly gathering headway. As her stern sank and finally the bow dipped into the water, cheers broke forth. Then a cloud of smoke hid her. There was an ominous silence. Was she wrecked, at last, after all? A puff of wind cleared the smoke.

"Just the friction of the ways--set the grease on fire," shouted Marlowe. "It always does that."

Wedges, sliding ways, and other parts of the cradle floated to the surface. The tide took her and tugs crept up and pulled her to the place selected for temporary mooring. A splash of a huge anchor, and there she rode--safe!

In the revulsion of feeling, every eye on the platform turned involuntarily to Kennedy. Marlowe, still holding his hand, was speechless. Marjorie leaned forward, almost hysterical.

"Just a moment," called Craig, as some turned to go down. "There is just one thing more."

There was a hush as the crowd pressed close.

"There's a conspiracy here," rang out Craig's voice, boldly, "a foreign trade war. From the start I suspected something and I tried to reason it out. Having failed to stop the work, failed to kill Marlowe--what was left? Why, the launching. How? I knew of that motor-boat. What else could they do with it? I thought of recent tests that have been made with express cruisers as mine- planters. Could that be the scheme? The air-boat scheme occurred to me late last night. It at least was worth trying. You see what has happened. Now for the reckoning. Who was their agent? I have something here that will interest you."

Kennedy was speaking rapidly. It was one of those occasions in which Kennedy's soul delighted. Quickly he drew a deft contrast between the infinitely large hulk of the Usona as compared to the infinitely small bacteria which he had been studying the day before. Suddenly he drew forth from his pocket the bullet that had been fired at Marlowe, then, to the surprise of even myself, he quietly laid a delicate little nail file and brush in the palm of his hand beside the bullet.

A suppressed cry from Rae Melzer caused me to recollect the file and brush she had missed.

"Just a second," raced on Kennedy. "On this file and brush I found spores of those deadly anaerobes--dead, killed by heat and an antiseptic, perhaps a one-per-cent. solution of carbolic acid at blood heat, ninety-eight degrees--dead, but nevertheless there. I suppose the microscopic examination of finger-nail deposits is too minute a thing to appeal to most people. But it has been practically applied in a number of criminal cases in Europe. Ordinary washing and even cleaning doesn't alter microscope findings. In this case this trifling clue is all that leads to the real brain of this plot, literally to the hand that directed it." He paused a moment.

"Yesterday I found that anaerobe cultures were being received by some one in the Belleclaire, and--"

"They were stolen from me. Some one must have got into my office, where I was studying them." Doctor Gavira had pressed forward earnestly, but Craig did not pause again.

"Who were these agents sent over to wage this secret war at any cost?" he repeated. "One of them, I know now, fell in love with the daughter of the man against whom he was to plot." Marjorie cast a furtive glance at Fitzhugh.

"Love has saved him. But the other? To whom do these deadly germs point? Who dum-dummed and poisoned the bullet? Whose own fingers, in spite of antiseptics and manicures, point inexorably to a guilty self?"

Rae Melzer could restrain herself no longer. She was looking at the file and brush, as if with a hideous fascination. "They are mine--you took them," she cried, impulsively. "It was she--always having her nails manicured--she who had been there just before-- she--Alma Hillman!"