Tired of reading? Add this page to your Bookmarks or Favorites and finish it later.
|
|
Cast iron, however, if subjected to only one single fusion,
is rarely sufficiently homogeneous; and it requires a second
fusion completely to refine it by dispossessing it of its last
earthly deposits. So long before being forwarded to Tampa Town,
the iron ore, molten in the great furnaces of Coldspring, and
brought into contact with coal and silicium heated to a high
temperature, was carburized and transformed into cast iron.
After this first operation, the metal was sent on to Stones Hill.
They had, however, to deal with 136,000,000 pounds of iron, a
quantity far too costly to send by railway. The cost of
transport would have been double that of material. It appeared
preferable to freight vessels at New York, and to load them with
the iron in bars. This, however, required not less than sixty-eight
vessels of 1,000 tons, a veritable fleet, which, quitting
New York on the 3rd of May, on the 10th of the same month ascended
the Bay of Espiritu Santo, and discharged their cargoes, without
dues, in the port at Tampa Town. Thence the iron was transported
by rail to Stones Hill, and about the middle of January this
enormous mass of metal was delivered at its destination.
It will easily be understood that 1,200 furnaces were not too
many to melt simultaneously these 60,000 tons of iron. Each of
these furnaces contained nearly 140,000 pounds weight of metal.
They were all built after the model of those which served for
the casting of the Rodman gun; they were trapezoidal in shape,
with a high elliptical arch. These furnaces, constructed of
fireproof brick, were especially adapted for burning pit coal,
with a flat bottom upon which the iron bars were laid. This bottom,
inclined at an angle of 25 degrees, allowed the metal to flow into
the receiving troughs; and the 1,200 converging trenches carried
the molten metal down to the central well.
The day following that on which the works of the masonry and
boring had been completed, Barbicane set to work upon the
central mould. His object now was to raise within the center of
the well, and with a coincident axis, a cylinder 900 feet high,
and nine feet in diameter, which should exactly fill up the
space reserved for the bore of the Columbiad. This cylinder was
composed of a mixture of clay and sand, with the addition of a
little hay and straw. The space left between the mould and the
masonry was intended to be filled up by the molten metal, which
would thus form the walls six feet in thickness. This cylinder,
in order to maintain its equilibrium, had to be bound by iron
bands, and firmly fixed at certain intervals by cross-clamps
fastened into the stone lining; after the castings these would
be buried in the block of metal, leaving no external projection.
|