of every German trench is marked to the inch on our officers' maps.
What do you think our aviators are for? Don't you know that they take
pictures of the enemy's fortifications from their machines and that all
the pictures are developed and enlarged? Oh, they'll have the range
all right. You'll see."

"Look!" cried Leon suddenly. "Here comes one of our aerial scouts now."

Far away in the eastern sky a tiny speck appeared. It approached
rapidly and increased in size as it came nearer. At least four
thousand feet above the trenches the great mechanical bird flew and the
three young soldiers watched it in silent admiration.

Suddenly a puff of white smoke appeared below the aeroplane.

"The Germans are firing at it," cried Earl.

"And there goes one of their machines up after it," exclaimed Jacques
as another speck appeared against the horizon. It was lower than the
French machine but rose in great circles with amazing speed until it
had reached a point above its enemy. At this point it headed west and
sped in pursuit of the French aeroplane.

"One of those new _fokkers_," remarked Jacques quickly.

"The German machine, you mean?" queried Leon.

"Yes. They are very fast too."

"He'll never come over our line though," said Earl. "He'll turn back
soon."

"There goes another of our machines up to help," exclaimed Leon.

From the aviation field in the rear of their quarters came a great
clatter and noise. A moment later a big monoplane came into view and
rising rapidly higher and higher set out to the aid of its companion.

Meanwhile the first aviator, pursued by the German _fokker_, had
evidently determined to give battle. He dipped suddenly and shot
downward at incredible speed. All about him the bombs from the
high-angle guns of the enemy were exploding and it did not seem
possible that he could escape. The cheering of their comrades in the
trenches came faintly to the ears of the three watching boys.

"He'll be hit," cried Leon tensely.

"Wait," cautioned Jacques.

The aeroplane still raced towards the earth. Suddenly it began to rise
and up, up, it soared. Higher and higher it went, describing huge
circles in its flight. The little white clouds all about told with
what zeal its destruction was sought, but still it kept on. Now it had
reached a level as high as the giant _fokker_. Meanwhile the other
French machine raced to its aid.

"You'll see the German turn back now," predicted