form a double skin to the ship, or a dermis and epidermis; the Leviathan is therefore two ships, one within the other. The whole framework forms a system of cells, which, like the Menai tube, combines extreme lightness with great strength.
So thoroughly close are the joints of this framework—we quote, with some modification, the words of a competent authority—that any one cell would hold water without its running into the adjoining cells; and water is actually to be admitted to some of them, to assist in ballasting or in "trimming" ship, or in giving it a "lift" or tilt-up when the bottom needs repair, taps and valves being arranged for that purpose. Above the level already named, five feet higher than low- water mark, the hull is formed of bars and plates as below; but it is not cellular, being only one layer in thickness. The various decks, whole and partial, are mostly formed of iron. The upper deck is so strong that it is calculated that the whole weight of the vessel might be suspended from it; like the lower part of the hull it has a cellular structure, and will help to maintain the bulging sides in their places, at the same time that it supports the visible wooden deck.
At the bow, or head of the vessel, the decks and partitions, the walls and casings, the supports and angle-irons are so numerous that the whole forms a mass nearly as strong as solid iron. To strengthen the interior of the mighty ship, to define its shape, and to separate it into water-tight compartments,
