"What is it?"

"Why, we'll stop right in the path taken by the enemy planes and then drop down upon the water."

"So the Germans can see us as they fly by, eh?"

"They won't see us in the dark," said Frank. "We'll be a pretty small spot down on the water. They will be looking for nothing so small."

"I guess you are right, after all," Jack agreed. "At least it's worth trying. We'll be sure to hear them flying above; and if we went beyond the lane of travel, or didn't go far enough, we might not even see them."

"Exactly," said Frank. "Well, there is no hurry, so I may as well slow down a bit."

He did so and they went along more leisurely.

"Can't see what the Germans would be flying about here for," said Jack, "and I have been trying to figure it out ever since I read that message."

"So have I," declared Frank, "If they were Zeppelins I could understand it; they would be going and returning from raids on the British coast; but surely they would not venture that distance with aeroplanes."

"I wouldn't think so. Still, you never can tell about those fellows.

They do a lot of strange things."

"So they do. Say!" Frank was struck with a sudden thought. "You don't suppose the presence of many of those fellows heralds the advance of the German fleet, do you? They might be just reconnoitering, you know."

"No, I hardly think that could be it. The Germans are afraid to venture out. They know they'll get licked if they do."

"Well, those aeroplanes come out every night for some purpose, that's sure," said Frank. "It's a wonder to me the Germans haven't tried to sneak out in great force before now. They could come along here without any trouble, or they could make the effort farther north, say near Jutland."

"Well, I suppose they'll try it some day," said Jack, "but not right away. How much farther do we have to go?"

Frank glanced at his chart and then at his speedometer.

"About fifteen miles," was his reply; "and then we'll be there too soon."

The lad was right. It was not three o'clock when the hydroplane came to the spot the lads had selected to descend.

"Well, here we are," said Frank.

"Guess we may as well go down, then," said Jack. "Some of those fellows are likely to be prowling about and spot us."

"Just as you say," agreed Frank.

He set the planes and the machine glided to the water, where it came to rest lightly.

"Glad there is no sun," said Jack, "it would be awfully hot down here."

And there the lads spent the afternoon. Darkness came at last, and with its coming, the lads made ready for whatever might occur. Eight o'clock came and there had been no sounds of airships flying above. The lads strained their ears, listening for the slightest sound.

And, shortly after nine o'clock, their efforts were rewarded. Jack suddenly took Frank by the arm.

"Listen!" he exclaimed in a low voice.

CHAPTER VII

AMONG THE ENEMY

To Frank's ears came a distant whirring. To ears less keen than the lad's the sound, which came from above, might have been some bird of the night flapping its wings as it soared overhead. But to Frank and Jack both it meant something entirely different. It was the sound for which they had been waiting. It was an airship.

Through his night gla.s.s Jack scanned the clouds and at last he picked up the object for which he sought. Almost directly overhead at that moment, but flying rapidly westward, was a single aeroplane. So high in the air was the machine that it looked a mere speck and Jack was unable to determine from that distance whether it was British or German.

"See it, Jack?" asked Frank in a low voice.

"Yes," was the reply. "A single craft, perhaps half a mile up."

"No more in sight, eh?"

"Not yet. This one is heading west."

"Guess we had better get up that way, then," said Frank.

Jack a.s.sented.

A moment later the hydroplane was skimming swiftly over the water. For perhaps three hundred yards Frank kept the craft on the water; then sent it soaring into the air above.

There was not a word between the two boys until the hydroplane was a quarter of a mile in the air. Then Jack said:

"Make your elevation half a mile and then head west, slowly. The chances are there will be more of them. In the darkness we can let them overtake us and mingle with them in safety."

Frank gave his endors.e.m.e.nt to this plan and the machine continued to rise. At the proper elevation, Frank turned the hydroplane's head westward and reduced the speed to less than thirty miles an hour. So slow was its gait, in fact, that it had the appearance of almost standing still.

Jack scanned the eastern horizon with his gla.s.s.

"See anything?" asked Frank.

"Thought I did," was the reply, "but whatever I saw has disappeared now. Guess I must have been mistaken."

But Jack had not been mistaken.

Far back, even now, a fleet of perhaps a dozen German air planes were speeding westward. For the most part they were small craft, having a capacity of not more than three men, with the single exception of one machine, which, larger than the rest, carried four men. The air planes were strung out for considerable distance, no two being closer than two hundred yards together.

And in this manner they overtook the hydroplane driven by Frank and Jack.

Jack, again surveying the horizon with his night gla.s.s, gave an exclamation.

"Here they come, Frank," he said. "Let her out a little more."

Frank obeyed without question and the speed of the hydroplane increased from something more than thirty miles an hour to almost sixty. And still the Germans gained.