ack over the American lines. They had no easy time reaching
them, for by this time the fleet of Hun planes had been defeated by the
Allies, and had turned tail to run for safety--that is what were left of
them, several having been shot down, and at no small cost to the French,
English and American forces.

But the defeat of their airmen seemed to anger the Germans, and they
opened up with their antiaircraft batteries on the machine in which Tom
and Jack were flying homeward. "Woolly bears" and "flaming onions," as
well as shrapnel, was used against them, and they were in considerable
danger. Jack had to "zoom" several times to get out of reach of the
shells.

They finally reached their aerodrome, however, and as soon as they had
landed and their plane was taken in charge by the mechanics the two lads
hurried to the commanding officer.

"Well?" he asked sharply, as they saluted. "Did you discover anything?"

"I think so, sir," returned Tom, for Jack had told his chum to do
the talking, since the discovery was his. "You remember, sir, the old
chateau we put out of business the other day?"

"Yes, I recall it. What about it?"

"This: It seems suddenly to have grown a wooded park around it, and
the trees and bushes don't seem to be as fresh as natural ones ought to
look."

"You mean they camouflaged the ruins, and have put another battery in
the old, chateau?"

"I think so, sir. It wouldn't do any harm to drop a few shells there.
If it's still a ruin the worst will be that we've wasted a little
ammunition and may start the German guns up. And if it is what we think
it is, we may blow up the battery."

The commander thought for a moment.

"I'll try it!" he suddenly said. "It's worth all it will cost."

He called an orderly and issued his instructions. Tom and Jack had not
yet been dismissed, and now the commanding officer turned to them and
said:

"Since you boys were sharp enough to discover this, I'll let you have a
front seat at the show which will start soon. Go up and do contact work.
Let the gunners know when they make a hit."

The air service boys could not have wished for anything better.

"Once more for our bus!" exclaimed Jack delightedly, when they were
outside.

Their Spad had been refilled with gasoline, or "petrol," as it is called
on the other side, and oil had been put in, while the machine guns had
been looked to.

"You seem to have spotted it all right, Tom," went on Jack, just as
they