bears," the latter a most
unpleasant object to meet in mid-air.

For the Germans were taking no chances. They knew the vulnerable
points of their prison camp lay above, and they had provided a ring of
anti-aircraft guns to take care of any Allied, machines that might fly
over the place. Whether any such daring scheme had been tried before or
not, Tom and Jack could not say.

Of course it was out of the question that any great damage could be done
in the vicinity of the camp without endangering the inmates, so it was
not thought, in all likelihood, that any very heavy air raids would have
to be repelled. But in any case, the Huns were ready for whatever might
happen.

"Better drop the bombs, hadn't we?" cried Jack to Tom, as he slowed down
the motor a moment to enable his voice to be heard.

"I guess so--yes. Drop 'em and then shoot over the camp again and let
the packages fall. It's getting pretty hot here."

And indeed it was. Guns were shooting at the two daring air service boys
from all sides of the camp.

In the camp itself great excitement prevailed, for the prisoners knew,
now, that it was some of their friends flying above them.

There was another danger, too. Not many miles away from the prison camp
was a German aerodrome, and scenes of activity could now be noticed
there. The Huns were getting ready to send up a machine--perhaps more
than one--to attack Tom and Jack.

It was, then, high time they acted, and as Jack again started the
engine, he guided the machine over a spot where the anti-aircraft guns
were most active.

"There's a battery there I may put out of business," he argued.

Flying fast, Jack was soon over the spot, or, rather, not so much over
it, as in range of it. For when an aeroplane drops a bomb on a given
objective, it does not do so when directly above, but just before it
reaches it. The momentum of the plane, going at great speed, carries
any object dropped from it forward. It is as when a mail pouch is thrown
from a swiftly moving express train or a bundle of newspapers is tossed
off. In both instances the man in the train tosses the pouch or his
bundle before his car gets to the station platform, and the momentum
does the rest.

It was that way with the bomb Jack released by a touch of his foot on
the lever in the cockpit of the machine. Down it darted, and, wheeling
sharply after he had let it go, the lad saw a great puff of smoke
hovering directly over the spot where, but a