. He
leaped out of his craft, and was about to ask for another to go back and
renew the battle of the clouds, when he saw the big photographing
machine returning, accompanied by all but two of the escorting craft.

"A pair missing," murmured the major, as he searched the sky with his
glasses.

And Tom wondered if Jack's machine was among those that had not headed
back.

Eagerly he procured a pair of binoculars, and when he had them focused
he identified one machine after another, at last picking out his chum's.
It did not seem to be damaged.

But two of the French craft had been brought down--one in flames, the
report had it, and the other out of control, and both fell within the
German lines.

"Did you get any photographs of the big gun?" asked the major, when the
men in the double machine had made a landing.

"We got lots of views," answered the photographer, "but what they show
we can't say. As far as having seen the gun goes, we didn't spot it."

"Well, maybe the photographs will reveal it," suggested the major. "Ah,
but I am sorry for the two that are lost!"

Jack's experience had been less exciting than Tom's. One machine had
attacked the former, and there had been a hot engagement for a while,
but the German had finally withdrawn, though to what extent he was
wounded or his machine damaged Jack did not know.

However, the picked squadron had reason to feel satisfied with their
efforts. All now depended on the developing of the photographs, and this
was quickly done. For this part of warfare is now regarded as so
important that it is possible for a plane to fly over an enemy's
station, take photographs and have prints in the hands of the commanding
officer inside of an hour, if all goes well.

Carefully the photographs were examined by men expert in such matters.
Eagerly they looked to discover some signs of the emplacement of the big
gun. But one after another of the experts shook his head.

"Nothing there," was the verdict.

"Then we've got to try again," decided Major de Trouville. "We must
find that gun and destroy it!"

"Well, we're ready," announced Tom, and the others of the picked
squadron nodded in assent.

And then began an organized campaign to locate the monster cannon. It
continued to fire on Paris at intervals. Then three days went by without
any shells falling, and the rumor became current that the gun had burst.
If this had happened, there was another, or more, to take its place,