From the Earth to the Moon, Direct in Ninety-Seven Hours and Twenty Minutes: and a Trip Round It. Verne Jules

will be easily understood that 1200 furnaces were not too many to melt simultaneously these 60,000 tons of iron. Each of these furnaces contained nearly 140,000 lbs. 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°, allowed the metal to flow into the receiving troughs; and the 1200 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 centre of the well, and with a coincident axis, a cylinder 900 feet high, and 9 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.