Directly the
finger is drawn out of the glove--in other words, immediately the
plunger is raised out of the cylinder--the latter drops down below
with a heavy thud, still in a red hot condition.
[Illustration: FIG 3.]
This operation of hot drawing is repeated again and again in rams of
diminishing size until the cylinder assumes the diameter and length
required. This hot drawing leaves the surface of the metal marked with
longitudinal lines, not unlike the glacier scratches on a rock, albeit
they are straighter and more regular. But the next operation not only
obliterates these markings, and gives the metal a smooth surface like
that of polished silver, but it also confers upon the material a
homogeneity which it did not before possess, and without which it
would never bear the pressure which it is destined to withstand when
finished. This operation consists in a final application of the
hydraulic ram while the metal remains perfectly cold, instead of red
hot, as in the previous cases.
As the result of these various hydraulic operations, we have a
perfectly formed cylinder closed at one end, and we now follow it into
another department of the works, when its open end is once more
brought in a furnace to a red heat.
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