"What do you suppose is in the half-open keg that you were sitting on?"
demanded Captain Jack, rather hoarsely.

"What!" queried the machinist, curiously.

"The head of that keg is half off," Jack continued. "Now, if any sparks
from your pipe had dropped down and set the bagging afire--well, that
keg is almost full of cubes of gun-cotton!"

"Whew!" gasped Williamson, beginning to look pallid himself.

"Nor is that all," Hal took up. "Of course, if you had touched off that
gun-cotton in the keg, it would have sent us all through the roof. But
the smaller explosion would have touched off the two tons and a half of
gun-cotton in those Whitehead torpedoes. That would have laid the whole
shipyard flat. In fact, after the torpedoes went up, there wouldn't have
been much left of any part of Dunhaven!"

"Gr--great Hercules!" gasped the machinist, his face now losing every
vestige of color.

Then, after a moment:

"With so much sky-high trouble stored in that shed, you should have a
sign up."

"There is one, on the door," replied Captain Jack. "But the door
happened to be swung open, so that you couldn't see it. Yet I guess
you're the only one in all Dunhaven who didn't know what the shed
contains."