"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.