s a case of waiting and hoping.

Jack was not yet permitted to fly, so Tom had to go alone. But he served
as an instructor, leaving the more dangerous work of patrol, fighting,
and reconnaissance to others until he was fit to stand the strain of
flying and of fighting once more.

"Sergeant Raymond, you will take up Martin to-day," said the flight
lieutenant to Tom one morning. "Let him manage the plane himself unless
you see that he is going to get into trouble. And give him a good
flight."

"Yes, sir," answered Tom, as he turned away, after saluting.

He found his pupil, a young American from the Middle West, who was not
as old as he and Jack, awaiting him impatiently.

"I'm to get my second wing soon, and I want to show that I can manage a
plane all by myself, even if you're in it," said the lad, whose name was
Dick Martin. "They say I can make a solo flight to-morrow if I do well
to-day."

"Well, go to it!" exclaimed Tom with a laugh. "I'm willing."

Soon they were in a double-seater of fairly safe construction--that is,
it was not freakish nor speedy, and was what was usually used in this
instructive work.

"I'm going to fly over the town," declared Martin, naming the French
city nearest the camp. "Well, mind you keep the required distance up,"
cautioned Tom, for there was, a regulation making it necessary for
the aviators to fly at a certain minimum height above a town in flying
across it, so that if they developed engine trouble, they could coast
safely down and land outside the town itself.

"I'll do that," promised Martin.

But either he forgot this, or he was unable to keep at the required
height, for he began scaling down when about over the center of
the place. Tom saw what was happening, and reached over to take the
controls. But something happened. There was a jam of one of the levers,
and to his consternation Tom saw the machine going down and heading
straight for a large greenhouse on the outskirts of the town.

"There's going to be one beautiful crash!" Tom thought, as he worked in
vain to send the craft up. But it was beyond control.

CHAPTER XVIII. GETTING A ZEPPELIN

Dick Martin became frantic when he saw what was about to happen. He
fairly tore at the various levers and controls, and even increased the
speed of the motor, but this last only had the effect of sending the
machine at a faster rate toward the big expanse of glass, which was the
greenhouse roof.

"Shut it off!