the former, being smaller, are more easily
concealed.

But Tom and Jack would, of course, do their best to help out their
friends, the French. Over toward the German lines they flew, and began
to scan with eager eyes the ground below them. They could not fly at a
very great height, as they needed to be low down in order to see, and in
this position they were a mark for the anti-aircraft guns of the Huns.

They had no sooner got over the enemy trenches, and were peering about
for the possible location of the machine gun emplacement, when they
were greeted with bursts of fire. But by skillfully dodging they escaped
being hit themselves, though their machines were struck. The two chums
were separated by about a mile, for they wanted to cover as much ground
as possible.

At last, to his great delight, Tom saw a burst of smoke from a building
that had been so demolished by shell fire that it seemed nothing could
now inhabit it. But the truth was soon apparent. The machine gun nest
was in the cellar, and from there, well hidden, had been doing terrible
execution on the allied forces. Pausing only to make sure of his
surmise, Tom began to tap out on his wireless key the location of the
hidden machine gun nest.

Most of the aeroplanes carry a wireless outfit. An aerial trails after
them, and the electric impulses, dripping off this, so to speak, reach
the battery headquarters. Owing to the noise caused by the motor of the
airship, no message can be sent to the airman in return, and he has to
depend on signs made on the ground, arrows or circles in white by day
and lighted signals at night, to make sure that his messages are being
received and understood.

The Allies, of course, possess maps of every sector of the enemy's
front, so that by reference to these maps the aircraft observer can send
back word as to almost the precise location of the battery which it is
desired to destroy.

Quickly tapping out word where the battery was located, Tom awaited
developments, circling around the spot in his machine. He was fired at
from guns on the ground below, but, to his delight, no hostile planes
rose to give him combat. A glance across the expanse, however, showed
that Jack was engaging two.

"He's keeping them from me!" thought Tom, and his heart was heavy, for
he realized that Jack might be killed. However, it was the fortune of
war. As long as the Hun planes were fighting Jack they would not molest
him, and he might have ti