trol, or in flames. But the Huns paid dearly for their quarry.

Jack and Tom ran serious risks, for the Germans, realizing that the two
leading planes had some special mission, attacked them fiercely. Tom
managed to shake off and disable his antagonist. But Jack's man shot
with such good aim that he pierced his gasolene tank, and had it not
been that Jack was able to thrust into the hole one of some wooden plugs
he had brought along for the purpose, he might have had to come down
within the German lines. But the wood swelled, filled the hole, and then
the petrol came out so slowly that there was comparatively little
danger.

And having, with some of their companions, fought their way through the
German air patrol, and having escaped with minor damage to their guns,
Jack and Tom looked down at the place where they had seen the queer
lights.

And then, high up and at a vantage point, while below them hovered their
photographing planes, the two young aviators beheld a curious sight.

In German-occupied territory, but on French soil, they saw near a
railroad junction, where they were fairly well hidden in a camouflaged
position, not one, but three monster Hun cannons. The guns looked more
like gigantic cranes than like the accepted form of a great rifled piece
of armament. The guns were so mounted that they could be run out on a
small track at the moment of firing, and then propelled back again, like
some of the disappearing cannon at Sandy Hook and other United States
forts. Only the German guns advanced and retreated horizontally, while
the usual method is vertically.

"We've discovered 'em! There they are!" cried Tom, but of course he
could not hear his own voice above the roar of his motor. But he knew
that he and Jack were over the very spot where the night before they had
seen the colored flares from the great guns.

And they had, indeed, by a most lucky chance, located the big German
guns, for there were three of them. They were placed almost midway
between the railroad station of Crepyen-Lannois and the two forts known
as "Joy Hills," forts which had fallen into German hands. There were
two railroad spur lines from the station, and on these the heavy guns
were moved to position to fire, and then run back again. Other spur
lines were under course of construction, Jack and Tom, as well as the
other airmen, could observe, indicating that other guns were to be
mounted, perhaps to take the place of some that might