ges 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 of
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 dangerous?" I asked, amazed at the skill with which he
handled the blowpipe.

"Not particularly--when you know how to do it. In that tan