If, for instance, it is desired to mend a broken rail or crank shaft
without moving it from its place, the two ends are brought together or
fixed at the proper distance apart. A crucible filled with the thermit
mixture is set up above the joint and the thermit ignited with a priming
of aluminum and barium peroxide to start it off. The barium peroxide
having a superabundance of oxygen gives it up readily and the aluminum
thus encouraged attacks the iron oxide and robs it of its oxygen. As
soon as the iron is melted it is run off through the bottom of the
crucible and fills the space between the rail ends, being kept from
spreading by a mold of refractory material such as magnesite. The two
ends of the rail are therefore joined by a section of the same size,
shape, substance and strength as themselves. The same process can be
used for mending a fracture or supplying a missing fragment of a steel
casting of any size, such as a ship's propeller or a cogwheel.
[Illustration: TYPES OF GAS MASK USED BY AMERICA, THE ALLIES, AND
GERMANY DURING THE WAR
In the top row are the American masks, chronologically, from left to
right: U.
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