"I can't move it!" Mr. Sharp yelled. "It's jammed! I can't shut off
the gas! Run! Look out! She'll explode!"

Tom Swift, the young inventor, whose acquaintance some of you have
previously made, gave one look at the gauge, and seeing that the
pressure was steadily mounting, endeavored to reach, and open, a stop-
cock, that he might relieve the strain. One trial showed him that the
valve there had jammed too, and catching up a roll of blue prints the
lad made a dash for the door of the shop. He was not a second behind
his companion, and hardly had they passed out of the structure before
there was a loud explosion which shook the building, and shattered all
the windows in it.

Pieces of wood, bits of metal, and a cloud of sawdust and shavings
flew out of the door after the man and the youth, and this was
followed by a cloud of yellowish smoke.

"Are you hurt, Tom?" cried Mr. Sharp, as he swung around to look back
at the place where the hazardous experiment had been conducted.

"Not a bit! How about you?"

"I'm all right. But it was touch and go! Good thing you had the gauge
on or we'd never have known when to run. Well, we've made another
failure of it," and the man spoke somewhat bitterly.

"Never mind, Mr. Sharp," went on Tom Swift. "I think it will be the
last mistake. I see what the trouble is now; and know how to remedy
it. Come on back, and we'll try it again; that is if the tank hasn't
blown up."