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GOLD. 21 I

it to repeated blows with a heavy hammer. Tt should be
frequently annealed, and the process of forging continued,
alternately hammering and annealing, until the ingot is
reduced one-half or more in thickness.
Laminating or Rolling.—The reduced ingot, well an-
nealed, is next rolled or spread out into a sheet of greater
or less thinness by passing it repeatedly bet^veen two strong,
highly-polished cylindrical steel rollers. The mills used for
the purpose are variously constructed, the plainest forms
being very simple in their mechanism, while others, or
Fig. 177.

geared mills, are more complicated, and are constructed wdth
a view to a greater augmentation of power, precision, and
certainty of action. Fig. 177 illustrates such a mill.
The rollers should first be adjusted equidistant at both
ends, and this uniformity, as they are approximated from
time to time, should be preserved throughout. At every
passage of the gold bar between the rollers, the distance