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 glass, 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.

"This will do," said Jack, leaning close to Frank. "They'll overtake
us, but believing we are of their number, there is little likelihood
that they will investigate us very closely. We can fall in line without
trouble and accompany them wherever they go."

"Suits me," said Frank. "Just keep me posted on their proximity."

Gradually the Germans reduced the distance and at length the first
plane was only a few yards behind the craft in which Frank and Jack
were risking their lives. The German craft flashed by a moment later
without paying any attention to the hydroplane.

"Little more speed, Frank," called Jack.

The hydroplane skimmed through the air faster than before and the next
German craft did not overtake it so easily; but at length it passed, as
did a third and a fourth.

"Here's a good place for us to fall in line," Jack instructed.

Again Frank increased the speed of the hydroplane and it moved swiftly
in the wake of the fourth German craft. After that no enemy air plane
passed them.

"Any idea where we are?" asked Frank of his chum.

"We're not far off the Belgian coast, but how far west I can't say,"
returned Jack. "Don't suppose it makes any particular difference,
though."

"I guess not."

Frank became silent and gave his undivided attention to keeping the
German plane ahead of him in sight.

And in this manner they proceeded for perhaps another half hour.

Then the machine ahead of Frank veered sharply to the south. Frank
brought the head of his own craft in the same direction and the flight
continued.

"Headed for the Belgian or French coast, apparently," said Jack to
himself. "Wonder what the idea is?"

Now the craft ahead of that in w