,
at a government school for aviation training, they had taken their first
lessons in flying, after the world war broke out. They decided to follow
that calling in case the United States should be eventually swept into
the war.

Tom's father was an inventor whose secret papers concerning a wonderful
airplane stabilizer had been stolen by an adroit German spy. Afterwards
the two chums when in France had managed to recover these documents, as
well as accomplish many other brilliant exploits, all this being told in
the first volume of this series, entitled: "Air Service Boys Flying for
France; or, The Young Heroes of the Lafayette Escadrille."

In the second volume Tom and Jack proved their right to be called
first-class air pilots by battling with success against Hun fliers. They
saw considerable of the tragic happenings that convulsed that portion of
France, while they were connected with the famous French flying corps.

Here, too, these young Air Service boys again found an opportunity for
proving their worth in the rescue of pretty Bessie Gleason and her
mother from an old chateau in Lorraine where Carl Potzfeldt, a German
spy, had them imprisoned. These interesting and exciting events will be
found in the second volume of the series, entitled: "Air Service Boys
Over the Enemy's Lines; or, The German Spy's Secret."

Then came another series of happenings that must always appeal to boy
readers fond of thrilling scenes, for in the next book, among many other
things, is told how Tom and Jack succeeded in silencing the monster
cannon that from a distance of sixty miles and more was bombarding
Paris. That will be found narrated in "Air Service Boys Over the Rhine;
or, Fighting Above the Clouds."

Then there is the volume just preceding this, in which again the two
brave young Yankee air pilots were given an opportunity to prove the
value of their training, now in the service of the American forces, for
General Pershing had come across the sea, and his army was beginning to
make its presence felt at several sectors of the battleline.

What they saw and did, as well as vivid descriptions of the momentous
events accompanying the great German drive is told in the fourth book
of the series, "Air Service Boys in the Big Battle; or, Silencing the
Big Guns."

Among their friends at the front was a young and daring aviator, Harry
Leroy by name, who had had the misfortune to be shot down behind the
German lines, and it was in