s heated at any point a furious struggle
takes place throughout the whole mass between the iron and the aluminum
as to which metal shall get the oxygen, and the aluminum always comes
out ahead. The temperature runs up to some 6000 degrees Fahrenheit
within thirty seconds and the freed iron, completely liquefied, runs
down into the bottom of the crucible, where it may be drawn off by
opening a trap door. The newly formed aluminum oxide (alumina) floats as
slag on top. The applications of the thermit process are innumerable.
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.S. Navy mask (obsolete), U.S. Navy mask (final type), U.S. Army
box respirator (used throughout the war), U.S.R.F.K. respirator,
U.S.A.T. respirator (an all-rubber mask), U.S.K.T. respirator (a sewed
fabric mask), and U.S. "Model 1919," ready for production when the
armistice was signed. In the middle row, left to right, are: British
veil (the original emergency mask used in April, 1915), British P.H.
helmet (the next emergency mask), British box respirator (standard
British army type), French M2 mask (original type), French Tissot
artillery mask, and French A.R.S. mask (latest type). In the front row:
the latest German mask, the Russian mask, Italian mask, British motor
corps mask, U.S. rear area emergency respirator, and U.S. Connell mask]

[Illustration: PUMPING MELTED WHITE PHOS