As he approaches these structures, he will notice many plates of superior iron from the rolling-mills of Baltimore, combining the toughness and strength and other excellences of the best Pennsylvania iron; he will notice, too, immense ribs and beams of iron, and hear the incessant din of hammers riveting the sides and boilers.
Under each of these sheds he will find an iron steamship, two hundred and seventy-five feet in length by twenty-three in depth, exquisitely proportioned; he will be struck by the fine entrance and run. The extreme sharpness of the stem and stern, combined with great capacity, seems to answer every requirement; and he will be surprised to learn that the draught of these steamers is but sixteen feet when deeply laden, and that their engines of thirteen hundred horse-power are expected to give them a speed of fifteen knots per hour. When they reach their destined element and have received their lading, the height from the water-line to the deck will be but seven feet; hence it is apparent that a belt of iron plates carried around them of eight feet four inches in height would protect them from the deck to a point sixteen inches below the water-line, or from the bottom of the deck-beams to a point two feet below the water-line.
The iron plates which form the sides of these ships range in thickness from one inch below the water-line to three-fourths of an inch above it. And if we allow for the superior strength and toughness of American iron, an additional plate of three inches in thickness would suffice to give them more strength than that of either the French or English mail-clad steamers.
By careful computation we have ascertained that each vessel might be encircled by such plates, weighing but one hundred and twenty pounds per superficial foot, and have her bulwarks plated also, without adding more than three hundred tons to her weight,—actually less than one-third of the cargo she was designed to carry. With an extra planking within, and an armament of twenty-four rifled fifty-pounders or Whitworth cannon, and select crews, such vessels need fear no antagonists upon the deep. Low in the hull, they would offer but little surface to the fire of the enemy, and their sides would be impervious to shot and shell. Beneath the decks they could carry in safety a whole regiment of troops. Selecting their position by superior speed, they could destroy a fleet of wooden steamers or ships-of-the-line. Entering any of our large seaports, they could pass the fortress at the entrance uninjured, and lay cities under contribution, or destroy their ports, without being, like Achilles, or the English "Warrior," vulnerable in the heel.
When such steamers come into general use, we shall hear no more of the wooden walls of Greece or England, or of those modern platforms which had not a stick of sound oak timber in them,—nothing, indeed, but pitch-pine and cypress. Oak, pine, and cypress would fall into the same category, when contrasted with the imperishable iron. Some new agency of steel must be invented to cope with the adamantine iron. And it becomes our Government, both for the armament of our ships and for defence against iron steamers, to adopt at the earliest moment every improvement in rifled cannon.
The Navy Department has recently put under contract seven steamships and several steam gun-boats. They have intrusted the latter to some of the ablest ship-builders of the country, and it is well understood that most of these vessels are to be completed the present season. This measure, as far as it goes, is eminently wise; but our navy must still be below the requirements of the nation, and entirely disproportioned to the extent both of our commerce and of our sea-coast. At a low estimate, our country requires an additional supply of at least six mail-clad steam frigates, twelve steam sloops-of-war, and twelve steam gun-boats, with similar armor. It will require also for long voyages and distant stations a dozen steam frigates of wood, and as many steam sloops-of-war, like the best now in our service; and, with the materials and armament now on hand, an outlay of twenty-five or thirty millions well applied may suffice for the construction of the whole. With such a provision we need feel no solicitude as to the intervention of England or France in our domestic affairs.
The lighter steamships of wood will answer for long voyages to the Mediterranean, the coast of Africa, India, and the Pacific, and will protect our grain, flour, and corn, on their way from the West to Europe. Our iron steamers will defend our commercial cities from attack or blockade; they will level all rebel batteries on the waters of the Chesapeake; they can batter down the fortresses of the Southern coast, and restore to commerce the ports of Charleston, Savannah, Pensacola, Mobile, Apalachicola, New Orleans, and Galveston.
Most fortunately for our country, at a moment when we cannot immediately command the live oak of Georgia and Florida, the oak plank of Virginia, or the yellow pine of the Carolinas, we have the most abundant supplies of iron easily accessible, and now, relieved from the demands of railways and factories, ready for the construction of our iron navy. The iron plates of Pennsylvania and Maryland in strength and toughness know no superior. The iron mountain near St. Louis and the mines on Lake Champlain furnish also an article of great purity and excellence. But, choice as are these deposits of iron, they are all surpassed by the more recent discoveries on Lake Superior, now opened by the ship-canal at the Straits of St. Mary. There Nature has stored an inexhaustible amount of the richest iron ore, free from sulphur, phosphorus, arsenic, and other deleterious substances, protruding above the surface of hillocks and underlying the country for miles in extent. This ore is of the specular and magnetic kind, yields sixty-five per cent. of iron of remarkable purity, is easily mined and transported to the Lake, and is shipped in vast quantities to the ports of Lake Erie, where it meets the coal of Ohio. At least ten companies are now engaged in its shipment, which has progressed thus far with great rapidity, doubling every year. The shipments from Lake Superior, in 1858, were thirty thousand five hundred and twenty-seven tons; in 1859, eighty thousand tons; in 1860, one hundred and fifty thousand tons. So great are the magnetic powers of this iron, that, buried as it was in the depths of the forest and beneath the surface of the earth, it disturbed the compasses of the United States surveyors while engaged in the survey of Northern Michigan. For a time their needle would not work, and they were obliged temporarily to suspend their operations. Their embarrassment led to the discovery of these vast deposits of ore. It is now mingled with the inferior ore of Ohio and Pennsylvania, and extensively wrought.
Our nation has strong motives to induce it to construct an iron navy.
First. The adoption of such a navy by the great powers of Europe,—England and France,—followed by Russia, Austria, and Spain. Our commerce will be in danger, if they once acquire the power of assailing us with impunity.