formation was found to be
so uniformly accurate that it was relied upon more and more as the
months went by.

CHAPTER XXI

The Great Coup

At the commencement of their work in the Secret Service, Max and Dale
visited Liege, and, while collecting information there, thought out and
put into operation a far-reaching plan that they hoped might checkmate
Schenk's schemes for the destruction of the Durend works when the
Germans should be forced to evacuate the city. It was a plan formulated
after they had again got into touch with M. Dubec and the small band of
men who still loyally refused to work in the interests of the invaders.
M. Dubec had imparted to them the information--not unexpected--that
Schenk had placed mines under all the workshops, and put everything in
readiness for blowing them into the air whenever he should wish to do
so.

"I have it from one of the men who actually helped to dig and fill them,
Monsieur. He was not allowed to help in the wiring, and he believes this
was done secretly at night, by Germans whom Schenk knew he could trust."

"So you know that the shops are mined, but do not know where the wires
run?"

"That is true, Monsieur."

"Could you not find out?"

"I do not think so, Monsieur. Since that last affair of ours there have
been too many sentries in the yards, especially at night. It would be
impossible to dig anywhere."

"We ought to do something, Dubec."

"Yes, Monsieur?"

"But the job is to know what," Dale struck in. "We can't tunnel
underground, I suppose, and get at them that way, so we must find out by
spying where the wires are run to--eh, Max?"

"Tunnel?" ejaculated Max. "That's an idea, Dale. Those old mines we were
tracing in the plans the other day! Why not?"

"Why not what?" asked Dale a little testily.

"Why, you know we noticed that one of them ran right up to the outskirts
of the city? Well, why shouldn't we continue it secretly, until we get
beneath the yards, and then burrow upwards to the workshops? Then we can
remove the mine-charges from below, and sit still and hold tight until
the great day arrives."

"Hurrah!" cried Dale enthusiastically. "The very thing. Phew! what a
coup it will be!"

"We shall, of course, have to get Dubec here and one or two others to
arrange it for us. They must go to work in the Durend mines, and take it
in turns to spend a night down there. Each man, as his turn comes, must
go into the old workings, and continue th