put the enemy to flight, and then for the signal that
would spell "homeward bound," a magical phrase with voyagers of the air
just as it is with sailors of the salty seas.

Finally it came. The great battle was over.

The air service boys rejoiced that the victory was won.

The roar of guns from below had ceased, and as the Yankees above could
not find any enemy plane against which to pit their strength, they, too,
no longer scurried this way and that, each one like an avenging Nemesis.

Looking down Jack was appalled at what he saw. It seemed almost as
though the end of the world had come. Huge volumes of acrid smoke slowly
swept along on the night air, with here and there a lurid tongue of
angry flame, looking like a serpent's tongue, stabbing the gloomy
curtain.

He had seen vivid pictures in colors of an eruption of Vesuvius, and to
his mind this presented just such an appalling spectacle. There could
never be any doubt regarding the awful power of those latest of Yankee
bombs. The German stronghold that an hour before had stood in arrogant
pride, meant to be a stumbling block in the path of Pershing's
victorious army, had been so shattered that it would hardly be noticed
in the general advance of the oncoming host of boys in khaki.

But there was the signal to gather once more in formation of twos for
the homeward journey. There would always be a chance that the furious
Huns might gather a fresh force of aerial fighters to make one last
assault on the columns before admitting defeat; and it was to be ready
for this that every possible precaution must be taken.

Then the fact became apparent that the return was not to be made with an
undiminished force. There were no longer exactly twenty planes to fill
out the double column. Some were missing, having fallen in the last
desperate attack of the foe, when a perfect whirlwind of fighting had
taken place.

Tom noticed this almost immediately. At least one battleplane was
absent, if not more, and the companion bomber that had occupied with
them the place of honor at the tail of the procession also failed to
come to its place. Perhaps the very plane he had watched drop and
wondered about was one of these missing ones.

Jack, too, looked down upon that vast smudge of smoke and shooting
flames with a new feeling gripping his heart. It no longer represented
merely the disappointed hopes of a Hindenburg and a Ludendorff; it was
not to be considered only a fortress