g, "set the oxygen there," as he placed his own
tank on the opposite side.

Out of the tanks stout tubes led, with stop-cocks and gages at the
top. From a case under his arm Kennedy produced a curious arrangement
like a huge hook, with a curved neck and a sharp beak. Really it
consisted of two metal tubes which ran into a sort of cylinder, or
mixing chamber, above the nozzle, while parallel to them ran a third
separate tube with a second nozzle of its own. Quickly he joined the
ends of the tubes from the tanks to the metal hook, the oxygen-tank
being joined to two of the tubes of the hook, and the second tank
being joined to the other. With a match he touched the nozzle
gingerly. Instantly a hissing, spitting noise followed, and an intense
blinding needle of flame.

"Now for the oxy-acetylene blowpipe," cried Kennedy as he advanced
toward the steel door. "We'll make short work of this."

Almost as he said it, the steel beneath the blowpipe became
incandescent.

Just to test it, he cut off the head of a three-quarter-inch steel
rivet--taking about a quarter of a minute to do it. It was evident,
though, that that would not weaken the door appreciably, even if the
rivets were all driven through. Still they gave a starting-point for
the flame of the high-pressure acetylene torch.

It was a brilliant sight. The terrific heat from the first nozzle
caused the metal to glow under the torch as if in an open-hearth
furnace. From the second nozzle issued a stream of oxygen under which
the hot metal of the door was completely consumed. The force of the
blast as the compressed oxygen and acetylene were expelled carried a
fine spray and the disintegrated metal visibly before it. And yet it
was not a big hole that it made--scarcely an eighth of an inch wide,
but clear and sharp as if a buzz saw were eating its way through a
three-inch plank of white pine. With tense muscles Kennedy held this
terrific engine of destruction and moved it as easily as if it had
been a mere pencil of light. He was easily the calmest of us all as we
crowded about him at a respectful distance.

"Acetylene, as you may know," he hastily explained, never pausing for
a moment in his work, "is composed of carbon and hydrogen. As it burns
at the end of the nozzle it is broken into carbon and hydrogen--the
carbon gives the high temperature, and the hydrogen forms a cone that
protects the end of the blowpipe from being itself burnt up."

"But isn't it dange