“Just how far does this practice go!” inquired the machinist, still sitting on the keg and smoking contentedly.

At that moment Captain Jack Benson caught, in his nostrils, the scent of burning tobacco.

In an instant a steely glitter shone in the young captain’s eyes.  Firm, strong lines appeared about his mouth.  All that part of the face showed white and pallid.  Just a second or two later Hal Hastings also turned.  Like a flash his lower jaw dropped, as though the hinge thereof had broken.

When Captain Jack’s voice came to him it sounded low, yet hard and metallic.  One would have wondered whether he had suddenly become ugly.

“Williamson,” he directed, “just step outside and see if Eph is there!”

Hardly noting the unusual ring in the young commander’s voice, the machinist, still with the pipe-stem between his teeth, rose and walked out into the open.  With an almost inarticulate yell Captain Jack Benson leaped after him, striking the man in the back and sending him spinning a dozen feet beyond.

Hal Hastings, too, dashed through the door way; then paused, grasping the edge of the door and shutting it with a bang.

“What on earth do you mean by knocking a fellow down like that?” demanded the machinist, angrily, leaping to his feet and wheeling about, leaving the lighted pipe on the snowcrust.

“Look at the sign on this door,” ordered Hal Hastings, pointing to the big white letters.

“Danger, eh?” asked Williamson, speaking more quietly.  “Well, that door was open and swung back when I came along, so I couldn’t see any warning.  But what is there in the shed that’s so mighty dangerous?”

“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.”