The writer is given to understand that the quantity of zinc recovered is
as high as from 50 to 60 per cent. of the total quantity used.
Although it was said that the rolling or milling of lead remains
unchanged in its main features since the first mill was established, yet
the writer's firm have introduced many important improvements. When lead
is required for sheet making, instead of running out the market lead
into the usual pigs of about one hundredweight each, it is run into
large blocks of 31/2 tons. These 31/2 ton blocks are taken on a bogie to
the mill-house, where the mill melting pot is charged with them by means
of a double-powered hydraulic crane, lifting, however, with the single
power only.
Three such blocks fill the pot, and when melted are tapped on to a large
casting plate, 8 ft. 4 in. by 7 ft. 6 in., and about 7 in. thick. This
block, weighing 101/2 tons, is lifted on to the mill table by the same
crane as fills the pot, but using the double power; and is moved along
to the rolls in the usual manner by means of a rope working on a surging
head. The mill itself, as regards the roll, is much the same as those
of other firms; but instead of an engine with a heavy fly-wheel, always
working in one direction, and connected to the rolls by double clutch
and gearing, the work is done by a pair of horizontal reversing engines,
in connection with which there is a very simple, and at the same time
extremely effectual, system of hydraulic reversing.
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