ight in this. The Germans had been thrown out of numerous
hard-won positions lately, and this gave them cause for feeling bitterly
toward the French.

By the time the American unit reached the field of battle, several
furious combats had already taken place with disastrous results. Two of
the enemy machines had been sent down, one of them in flames, after the
pilot had fallen at his post, fairly riddled by the gunfire of the
Frenchman. A birdman had also paid the great debt on the side of
Petain's men. As the score was two against one there seemed no cause for
depression.

The Americans would not be kept out of the fight for long. No sooner
were three adventurous Teuton pilots seen climbing up to attack the big
fire control machine when Tom's companions dropped down from the
"ceiling" to engage them.

Tom watched everything as though photographing the thrilling happenings
on his brain forever. He had a greater interest in these things than at
any previous period of his life, for was he not also hovering over that
observation Caudron, upon which the movements of the advancing French
troops depended? At any minute might he not receive the signal from the
captain to attack some fresh Boche, who had climbed high above the
battle lines to join the general scrimmage, or else "get" the big French
machine while its defenders had their hands full with his comrades?

Had Tom been able to use his binoculars just then, which was out of the
question of course, and look back to where the monster French guns were
firing, he might have noticed various white sheets spread out in
fantastic patterns on the ground, the picture varying every little
while.

These were used to "talk" with the observer who was sending those
messages from the fire-control plane, telling the gunners just how many
metres their fire was short, long, to the right, or to the left of their
intended objective.

Then again information was being sent by another observer to the
advancing infantry, warning them of perils that lay in their way, which
might have cost them great and grievous losses if they remained unknown
until the German trap was sprung.

The morning was advancing. Tom had seen his comrades chase off several
flocks of enemy aircraft that endeavored to interrupt the deadly work of
the observers. As yet his anticipated chance had not come. He was
beginning to feel impatient. Could it be that he must stay there almost
up among the clouds, and only be