livid and beaded with perspiration. He wiped it with
a shaking hand.

"Nevertheless you startled me," he said. "The sound the machine makes
has a frightful menace in it!" Then he looked at his watch. "It is now
eleven."

Vard nodded, and bent again above his apparatus, touching it here and
there with the touch of a lover--tightening a wire, examining a contact,
testing the vibrator....

His usual pale face was flaming with excitement, and his eyes shone with
a strange fire.

Marbeau glanced at him uneasily, then stared out at the grey wall of the
arsenal. Upon its summit a sentry walked to and fro with the precision
of a machine. High above him flapped the imperial flag of Germany,
displaying its eagles and complacent motto. Marbeau, like every
Frenchman, considered that flag an insult, for the lower arm of its
cross bore the date "1870," and he stared out at it now, dreaming of the
future, dreaming of the day when France should tear it down....

Vard touched him on the arm.

"I should like to see the plan of the fort again," he said.

Marbeau opened his shirt, and from a little oilskin bag produced a
square of tracing-paper. He unfolded it and handed it to the inventor.

"This is the side toward us," he said. "There are the magazines, the
main one being here in the centre."

With a nod of understanding, Vard carried the drawing to the window and
compared it carefully with the stretch of wall, swinging his pivoted
machine from side to side to be sure that its range was ample. Then he
refolded the map and returned it to Marbeau.

"It must be almost the hour," he said.

With a start, Marbeau pulled out his watch. It showed fifteen minutes to
twelve. Then, watch in hand, he stood gazing out at the bastion. Four
minutes passed, five, six, seven....

Suddenly from the fort came the deep boom of an alarm gun. A minute
later, a file of men appeared upon the summit of the bastion; a gate,
away to the right, swung open and an armed battalion marched out at the
double-quick.

"The signal!" gasped Marbeau. "It is the signal! Their wireless men have
picked it up!"

Again the alarm gun boomed sullenly, and they could hear the faint,
shrill calling of a bugle. Then came the distant thunder of the
answering guns from the forts about the town; from the streets rose
excited voices, the clatter of running feet....

One minute--two--three--

"Now!" said Marbeau, snapped shut his watch and thrust it into his
pocket.