late
extended for only a short distance. Around this, and spreading beneath
it, was a bed of cement. As soon as he had satisfied himself of that,
using Arthur's flashlight, Paul stopped digging, and began carefully to
replace the earth. Then, calling on Arthur to help him, he trampled
down the earth.

"There!" he said. "I don't believe anyone would know we had been here,
unless they were suspicious already."

"But what is it?" asked Arthur. "Paul, tell me!"

"I'm going to, Arthur. Don't worry. But come away from here. We
don't want to be caught around here--and, besides, there's still a good
deal for us to do."

Swiftly they made their way to the road, away from the cottage and the
field where they had made their discovery.

"Now!" said Arthur, after a little distance had been covered, stopping
short. "I won't go a step further until you tell me what that place is
meant for!"

"It's meant for a big gun--that's what it's meant for!" said Paul,
vehemently. "Can't you see? A siege gun can't be fired from a
carriage, or even from ordinary ground. The recoil would bury it in
the earth if they tried that. There's got to be a regular emplacement
for it--a firm base of concrete and steel, so that it will withstand
the shock of firing!"

"You mean they'd mount a gun here?"

"I mean just that! It takes days, almost weeks, to do that. They have
to pour the concrete and let it stand until it's set. But here they've
got everything ready! They can bring up their guns, place them, and
begin firing, all in less than twenty-four hours! They must have been
preparing for this for months--perhaps for years!"

"The cowards! We've never done anything to them!"

"No, they're not cowards," said Paul, thoughtfully. "I suppose they
think they're right, and that as long as that is so, they are justified
in using any means at all to win. But I think we can put a spoke in
their wheel, just the same."

"I don't see how, Paul. There aren't enough soldiers in Liege to watch
every spot where there's a cross marked on these maps."

"No, but that's not the only way, Arthur."

"It's the only way to stop them from bringing up their siege gun, isn't
it? I know what the plan is in case of an attack. It is for the forts
to hold off the Germans until there's time for the French army to come
up and relieve them. And they're not supposed to be able to stand the
fire of heavy guns. The plan was made for use against an ar