"That would be the natural course for such craft to take," agreed Admiral Wheatleigh. "I trust that you are right in your surmises. If you are, we should have some excellent results within the next few days."
"I shall know, sir, within forty-eight hours, and I think it likely that the enemy will also hear something about it within the next few days. At least, sir, the German admiralty should be able to guess."
Dave took his leave, hastening back to the "Grigsby," which, an hour later, weighed anchor and stood out to sea. By that time Dave was sound asleep, for he had been through a great deal and was sorely in need of rest before he reached the scene of his intended activities.
Some hours later he was called, and was soon on the bridge.
"You are at the point at which you wished to be called," said Fernald when Dave reached the bridge.
"And you will do well to seek your own rest now, Mr. Fernald," Darrin answered. "You can be called, if needed."
Half an hour later Darrin made out, in the sky astern, a tiny speck that rapidly came closer, and proved to be the dirigible sent at his request.
As the dirigible came nearer signals were rapidly exchanged. The course for the aircraft was made plain. As for the "Grigsby," her speed was slowed down to mere headway and she loafed over the waters.
Two hours pa.s.sed during which the "blimp" aloft sailed rapidly to and fro in the sky, zig-zagging over the course in a way that covered several square miles in an hour.
"She"s found something, sir!" cried Ensign Andrews.
"She has sighted a craft, bound over the course we had suspected," said Darrin, as signals broke out rapidly from the car under the big gas bag.
"We"ll let the submarine get by us before we start in chase."
Another half hour pa.s.sed, for, though the dirigible moved swiftly, the underseas craft she was watching was moving only at submerged speed.
Then the chase led on past the "Grigsby." Purposely Darrin allowed it to go by him by about a mile ere he joined in the pursuit. Starting at half speed ahead he soon changed it to full speed.
And now the dirigible had slowed down, until she was travelling, as her signals stated, at just the speed of the submerged craft directly under her.
"We"ll go in by the stern and try to make a quick job of it," Darrin proposed, as he gave Andrews final instructions, and turned to see that the signalman with his flag stood well aft on the superstructure.
As the destroyer raced in almost under the dirigible Darrin raised his right hand. The signalman with the flag did the same.
Just as the "Grigsby"s" bridge pa.s.sed in under the tail of the aircraft Dave Darrin read the signal for which he had waited. The airmen were telling him that the bridge of his craft was almost over the bow of the hidden enemy beneath.
Down came Dave"s raised hand. Seeing it fall, the signalman let his flag drop.
In that same instant the depth bomb was released for its course over the "Grigsby"s" stern.
Almost in the same second there sounded a terrific if m.u.f.fled report under the surface. The water rose in three distinct columns, lifting the stern of the "Grigsby" and almost burying her bow under.
It was as though a great geyser and an earthquake had met. Columns like waterspouts hurled themselves across and over the reeling destroyer. Even when the "Grigsby"s" nose came out and up once more the destroyer rocked in the near tidal wave that the swift series of explosions had produced.
"Pardon me, sir," begged Ensign Andrews, when he had regained control of himself. "I feel constrained to remark, sir, that you appear to know how to get all the thrills out of life."
"We must have landed right over a mine cargo once more," Dave answered smiling. "There were several explosions, but they came nearly together.
One of these days we"ll start something like that that will send us up half a mile into the air. But it"s great sport, Andrews, especially when you pause to think what it all means."
"Great sport for us, but too sudden for the Huns," rejoined the watch officer. "They cannot have had the satisfaction, even, of realizing that anything had hit them."
Satisfied that there would be no more underseas explosions, Darrin gave the order to come about.
That the underseas craft had been struck was indicated clearly enough by the patches of oil on the water. The force of the explosion told the Yankee tars that the craft must have been blown into bits.
"Best thing I ever saw done!" signalled the British officer in command of the "blimp."
"Find us another, and we"ll try to show you something just as good,"
Darrin caused to be signalled back.
Fernald, who had been called, having reported, was sent with the chief engineer to make a hull inspection below decks. Though some of the hull plates had been dented inward enough to attract attention, no leak could be found. The "Grigsby" was as seaworthy as ever, though after that rocking shock this seemed a marvel.
Off in the distance the "blimp" soon became a mere speck to the watchful eyes of those on the destroyer.
Dave directed that the aircraft be followed at cruising speed so long as she remained in sight. When the dirigible was at last lost to view the destroyer lay to, her lookouts using their gla.s.ses.
"Think the aircraft is coming back, sir," reported a lookout from the military mast.
From where he stood on the bridge Darrin could make out nothing for several minutes, though in the interval the lookout aloft reported that he could make out the "blimp" with surety, and that she appeared to be flying a signal, though he could not see what it was.
Then from the bridge the "blimp" became visible. A little later, too, the flag signal could be seen and read.
"Following another submarine," was what the signal said.
Going to starboard of the course Darrin advanced at ordinary speed to meet the "blimp," which, as in the former case, was flying just barely astern of the hidden monster, so that the forward British airman lookout could discern the shape of the craft that was being pursued.
Dave waited until the dirigible had pa.s.sed. He then gave the order, "Full speed ahead," and came about behind the "blimp."
Leaping forward the "Grigsby" gave chase, the "blimp" at the same time moving up directly over the intended prey.
At the drop of the flag above, Darrin let go his right hand, the signalman transmitted the order, and the bomb rolled overboard.
As Dave"s hand fell the watch officer advanced the lever of the engine-room telegraph. An extra jump was put into the speed.
Again a column of water rose astern, but this time there was only the normal explosion of the depth bomb.
"Good hit," said the dirigible, by radio, and the message was called up to the bridge. "Saw her stagger. She"s done for."
The "blimp" veered off once more, going back over her late course. As the "Grigsby" went about Darrin made out the tell-tale spread of oil on the waves.
"This is the real form of hunting," he exclaimed.
"Too bad, sir, that none of us thought of it before," remarked Ensign Andrews.
"We had to wait and learn," Dave explained. "That"s the way that all progress in this war has been registered. We are fighting an ingenious enemy. Destroying the submarine mine-carriers, as we are doing today, won"t end the planting of German mines. As soon as the enemy finds out how we are checkmating him he"ll invent another scheme, which we"ll have to discover before we can beat it."
Half an hour later the British aircraft located a third submarine.
"A big one, too," she signalled. "Following the same course."
"Mr. "Blimp" might try a bomb himself," suggested Ensign Andrews. "I believe he carries a few."