Burke, who liked a good detective tale himself, seemed pleased at holding Kennedy spellbound.
"For instance," he went on, "he has on the bay up here a submarine which can be made into a crewless dirigible. He calls it the Turtle, I believe, because that was the name of the first American submarine built by Dr. Bushnell during the Revolution, even before Fulton."
"You have theories of your own on the case?" asked Craig.
"Well, there are several possibilities. You know there are submarine companies in this country, bitter rivals. They might like to have those plans. Then, too, there are foreign governments."
He paused. Though he said nothing, I felt that there was no doubt what he hinted at. At least one government occurred to me which would like the plans above all others.
"Once some plans of a submarine were stolen, I recall," ruminated Kennedy. "But that theft, I am satisfied, was committed in behalf of a rival company."
"But, Kennedy," exclaimed Burke, "it was bad enough when the plans were stolen. Now Captain Shirley wires me that some one must have tampered with his model. It doesn't work right. He even believes that his own life may be threatened. And there is scarcely a real clue," he added dejectedly. "Of course we are watching all the employés who had access to the draughting-room and tracing everybody who was in the building that night. I have a complete list of them. There are three or four who will bear watching. For instance, there is a young attaché of one of the embassies, named Nordheim."
"Nordheim!" I echoed, involuntarily. I had expected an Oriental name.
"Yes, a German. I have been looking up his record, and I find that once he was connected in some way with the famous Titan Iron Works, at Kiel, Germany. We began watching him day before yesterday, but suddenly he disappeared. Then, there is a society woman in Washington, a Mrs. Bayard Brainard, who was at the Department that night. We have been trying to find her. To-day I got word that she was summering in the cottage colony across the bay from Lookout Hill. At any rate, I had to go up there to see the captain, and I thought I'd kill a whole flock of birds with one stone. The chief thought, too, that if you'd take the case with us you had best start on it up there. Next, you will no doubt want to go back to Washington with me."
Lookout Hill was the name of the famous old estate of the Shirleys, on a point of land jutting out into Long Island Sound and with a neighbouring point enclosing a large, deep, safe harbour. On the highest ground of the estate, with a perfect view of both harbour and sound, stood a large stone house, the home of Captain Shirley, of the United States navy, retired.
Captain Shirley, a man of sixty-two or three, bronzed and wiry, met us eagerly.
"So this is Professor Kennedy; I'm glad to meet you, sir," he welcomed, clasping Craig's hand in both of his—a fine figure as he stood erect in the light of the portecochére. "What's the news from Washington, Burke? Any clues?"
"I can hardly tell," replied the secret service man, with assumed cheerfulness. "By the way, you'll have to excuse me for a few minutes while I run back into town on a little errand. Meanwhile, Captain, will you explain to Professor Kennedy just how things, are? Perhaps he'd better begin by seeing the Turtle herself."
Burke had not waited longer than to take leave.
"The Turtle," repeated the captain, leading the way into the house. "Well, I did call it that at first. But I prefer to call it the Z99. You know the first submarines, abroad at least, were sometimes called A1, A2, A3, and so on. They were of the diving, plunging type, that is, they submerged on an inclined keel, nose down, like the Hollands. Then came the B type, in which the hydroplane appeared; the C type, in which it was more prominent, and a D type, where submergence is on a perfectly even keel, somewhat like our Lakes. Well, this boat of mine is a last word—the Z99. Call it the Turtle, if you like."
We were standing for a moment in a wide Colonial hall in which a fire was crackling in a huge brick fireplace, taking the chill off the night air.
"Let me give you a demonstration, first," added the captain. "Perhaps Z99 will work—perhaps not."
There was an air of disappointment about the old veteran as he spoke, uncertainly now, of what a short time ago he had known to be a certainty and one of the greatest it had ever been given the inventive mind of man to know.
A slip of a girl entered from the library, saw us, paused, and was about to turn back. Silhouetted against the curtained door, there was health, animation, gracefulness, in every line of her wavy chestnut hair, her soft, sparkling brown eyes, her white dress and hat to match, which contrasted with the healthy glow of tan on her full neck and arms, and her dainty little white shoes, ready for anything from tennis to tango.
"My daughter Gladys, Professor Kennedy and Mr. Jameson," introduced the captain. "We are going to try the Z99 again, Gladys."
A moment later we four were walking to the edge of the cliff where Captain Shirley had a sort of workshop and signal-station.
He lighted the gas, for Lookout Hill was only on the edge of the town and boasted gas, electricity, and all modern improvements, as well as the atmosphere of old New England.
"The Z99 is moored just below us at my private dock," began the captain. "I have a shed down there where we usually keep her, but I expected you, and she is waiting, thoroughly overhauled. I have signalled to my men—fellows I can trust, too, who used to be with me in the navy—to cast her off. There—now we are ready."
The captain turned a switch. Instantly a couple of hundred feet below us, on the dark and rippling water, a light broke forth. Another signal, and the light changed.
It was moving.
"The principle of the thing," said Captain Shirley, talking to us but watching the moving light intently, "briefly, is that I use the Hertzian waves to actuate relays on the Z99. That is, I send a child with a message, the grown man, through the relay, so to speak, does the work. So, you see, I can sit up here and send my little David out anywhere to strike down a huge Goliath.
"I won't bore you, yet, with explanations of my radio-combinator, the telecommutator, the aerial coherer relay, and the rest of the technicalities of wireless control of dirigible, self-propelled vessels. They are well known, beginning with pioneers like Wilson and Gardner in England, Roberts in Australia, Wirth and Lirpa in Germany, Gabet in France, and Tesla, Edison, Sims, and the younger Hammond in our own country.
"The one thing, you may not know, that has kept us back while wireless telegraphy has gone ahead so fast is that in wireless we have been able to discard coherers and relays and use detectors and microphones in their places. But in telautomatics we have to keep the coherer. That has been the barrier. The coherer until recently has been spasmodic, until we had Hammond's mercury steel-disc coherer and now my own. Why," he cried, "we are just on the threshold, now, of this great science which Tesla has named telautomatics—the electric arm that we can stretch out through space to do our work and fight our battles."
It was not difficult to feel the enthusiasm of the captain over an invention of such momentous possiblities, especially as the Z99 was well out in the harbour now and we could see her flashing her red and green signal-lights back to us.
"You see," the captain resumed, "I have twelve numbers here on the keys of this radio-combinator—forward, back, stop propeller motor, rudder right, rudder left, stop steering motor, light signals front, light signals rear, launch torpedoes, and so on. The idea is that of a delayed contact. The machinery is always ready, but it delays a few seconds until the right impulse is given, a purely mechanical problem. I take advantage of the delay to have the message repeated by a signal back to me. I can even change it, then. You can see for yourself that it really takes no experience to run the thing when all is going right. Gladys has done it frequently herself. All you have to do is to pay attention,