m. The American artillery and
machine guns swept the bridge with a withering fire. The front ranks
melted away like mist.

But their places were filled with others and still others, despite the
frightful slaughter. The American machine guns got too hot to handle
from their unceasing fire.

And still the German horde kept crowding forward as though their
reserves were inexhaustible. It was known that they had been heavily
reinforced of late and that they largely outnumbered the American
troops opposed to them. Over the dead bodies of their comrades which
strewed the bridge they were creeping nearer, urged by the irresistible
pressure from behind. Considering the disparity of forces, it was
sound tactics to destroy the bridge before the foremost ranks could get
a footing on the side where their overwhelming numbers would begin to
tell.

The American commander gave the order to blow up the bridge. But when
the button was pressed that should have sent the electric current into
the powder mine there was no response.

Several times the pressure was repeated and still no explosion
followed. A hasty consultation ensued between the leaders who were
standing close by the place where the Army Boys were fighting.

"The electric wires must have been cut by the enemy's fire," Frank
heard one of them say.

Cut! Then all the elaborate plans for blowing up the bridge had come
to naught. And that apparently inexhaustible gray force was getting
nearer and nearer!

CHAPTER XIX

THE JAWS OF DEATH

"There's just one possible chance," said Frank's colonel.

"What is that?" asked the general in command.

"An explosive bullet sent into the mine might explode it," replied the
colonel. "But it would have to be fired from a boat. We can't do it
from here."

"It would be certain death to whoever tried it," replied the general,
looking at the shell-swept stream.

"Not certain, perhaps, but probable," said the colonel. "It's the only
chance, though, to explode the mine. It can only be reached from
underneath."

"We'll try it," said the general with decision. "But I won't assign
any one to it. It's a matter for volunteers."

When the call came for volunteers, Frank sprang forward and saluted.
Bart and Billy followed close behind him.

The officer's eye swept the three and rested on Frank.

"You volunteer?" he asked. "You know the danger?"

"Yes, sir," they responded.

A gleam of pride and admiration ca