k is a porous
asbestos packing saturated with acetone, under pressure. Thus I can
carry acetylene safely, for it is dissolved, and the possibility of
explosion is minimised. This mixing chamber by which I am holding the
torch, where the oxygen and acetylene mix, is also designed in such
a way as to prevent a flash-back. The best thing about this style of
blowpipe is the ease with which it can be transported and the curious
uses--like the present--to which it can be put."

He paused a moment to test the door. All was silence on the other side.
The door itself was as firm as ever.

"Huh!" exclaimed one of the detectives behind me, "these new-fangled
things ain't all they're cracked up to be. Now if I was runnin' this
show, I'd dynamite that door to kingdom come."

"And wreck the house and kill a few people," I returned, hotly resenting
the criticism of Kennedy. Kennedy affected not to hear.

"When I shut off the oxygen in this second jet," he resumed as if
nothing had been said, "you see the torch merely heats the steel. I can
get a heat of approximately sixty-three hundred degrees Fahrenheit, and
the flame will exert a pressure of fifty pounds to the square inch."

"Wonderful!" exclaimed O'Connor, who had not heard the remark of his
subordinate and was watching with undisguised admiration. "Kennedy, how
did you ever think of such a thing?"

"Why, it's used for welding, you know," answered Craig as he continued
to work calmly in the growing excitement: "I first saw it in actual
use in mending a cracked cylinder in an automobile. The cylinder was
repaired without being taken out at all. I've seen it weld new teeth and
build up old worn teeth on gearing, as good as new."

He paused to let us see the terrifically heated metal under the flame.

"You remember when we were talking on the drive about the raid,
O'Connor? A car-load of scrap-iron went by on the railroad below us.
They use this blowpipe to cut it up, frequently. That's what gave me the
idea. See. I turn on the oxygen now in this second nozzle. The blowpipe
is no longer an instrument for joining metals together, but for
cutting them asunder. The steel burns just as you, perhaps, have seen
a watch-spring burn in a jar of oxygen. Steel, hard or soft, tempered,
annealed, chrome, or Harveyised, it all burns just as fast and just as
easily. And it's cheap too. This raid may cost a couple of dollars, as
far as the blowpipe is concerned--quite a difference from the