New-York, Jan. 31, 1862.The Ericsson Floating Battery, for the United States Government, was yesterday safely launched from the Continental Iron Works, Greenpoint, where it has been building for the last three months. The launch took place at about ten o'clock in the morning. Notwithstanding the early hour, the drizzling rain, the wretched state of travelling in the streets, and the fact that no notice had been given of the intended event, a very large crowd had collected along the wharf, consisting of workmen, residents of the neighborhood, and many persons of prominence in naval affairs, who had watched the undertaking with interest from its inception. In consequence of the novel construction of the vessel, and the vast amount of iron upon her, there was much anxiety felt as to the possibility of making her float, and it was strenuously maintained by many — and bets were offered and taken on the question — that she would sink as certainly as she was launched into the water. It was held to be impossible that a vessel of such light draft could carry such an enormous load of armor. At ten minutes before ten o'clock the braces were knocked away, and the vessel began to move slowly towards the water. The Stars and Stripes, floating from each end, began to flutter and to catch the breeze as she started. There were very few persons upon her deck, most of the spectators preferring to remain on shore. Those few stood near the stern, and had a small boat by them as a last resort in case the battery should make a dive to the bottom, and obstinately refuse to float. An important difficulty to be experienced in her launching arose from the fact that she was launched over a bulkhead, rendering her more liable to dip her bows into the sea, or to strain herself, than in any other case. Capt. Ericsson, however, showed his confidence in the structure which he had builded, and stood within twenty feet of the stern, risking, with evident unconcern, the ducking which was confidently anticipated  for him as soon as the bows struck the water. Amidst the greatest anxiety on shore and on board, the vessel moved easily into the water, not immersing more than six feet of her forward deck, and sailed gracefully out into the stream for some distance. It was very evident to the dullest observer, that the battery had not the slightest intention of sinking, being more than three feet out of water; and Captain Ericsson was delighted to find that she drew considerably less than his calculations had led him to anticipate. The anxiety gave way to enthusiasm, and all cheered to the best of their ability, including, to their credit be it said, those who had lost money by bets on the certainty of her sinking, and the waving of hats and handkerchiefs from the shore was answered by the jubilant passengers on the vessel in the stream. The workmen, who have taken the greatest interest in their work, and have a personal pride and confidence in the battery, were very enthusiastic. As soon as possible the vessel was brought to the dock and made fast there, giving many of the spectators an opportunity to go on the deck and observe her construction more closely. The whole work of the launch was accomplished in a very little time, and the crowd soon dispersed, satisfied with the success of the undertaking thus far. The vessel has been constructed with the specific intention of attaining absolute invulnerability under the guns of the most powerful batteries. It has been the endeavor, therefore, of the inventor to leave no part of the structure without adequate protection against all the possibilities of assault by shot and shell. The plan is entirely new and novel, and it is claimed that it fulfils every requirement of naval warfare more perfectly than is the case with any existing floating battery. There are, in effect, two hulls to the vessel. The lower one, which is entirely under water, is about six feet deep, built lightly, flat-bottomed, sharp at both ends, and with sides inclining at an angle of fifty-one degrees to the vertical line. The second or upper hull comprises the defensive portion, has straight sides, is longer and broader than the under one, is five feet deep, sinks into the water three feet and three inches, and is covered with heavy iron armor. It has no bottom excepting what is required to enable it to fit exactly on the top line of the lower hull, both, of course, forming the consecutive side of the vessel. Upon the deck, which is shell-proof, is a cylindrical turret, which is to contain and protect the guns. A screw propeller, aft of the raking stem of the lower hull, supplies the motive power against the water, and aft of the propeller is an equipoise rudder, both hidden under and protected by the upper hull. The engine, boilers, and blowers are also in the lower part and protected by the upper. The upper hull is one hundred and seventy-four feet long, forty-one feet four inches wide, and five feet deep. The stem and stern are pointed at an angle of eighty feet, and its sides are perpendicular. The sides are composed of a bulwark of white oak, thirty inches thick, fastened without bolts, upon which is placed an armor of rolled plate-iron six inches thick, extending from bottom to top of the straight side, of five feet depth, and all around the vessel. This will be submerged three feet and three inches, thus projecting only twenty-one inches above the water line. According to the original estimate of Capt. Ericsson the vessel was expected to draw ten feet, and project above the water-line only eighteen inches. But the actual presence of the vessel in the water yesterday proved that she will draw about three inches less than was estimated, or nine feet and nine inches. After the launch the vessel drew only seven feet three inches forward, and eight feet one inch aft; and as the additional weight of iron plating around the turret, the guns, and the fuel, which are to be put on the vessel, is accurately known, it has been estimated from these data that she will draw only the depth mentioned-nine feet nine inches. The deck is shell-proof, and is composed of plank eight inches thick, placed on oak beams ten inches square, twenty-six inches apart, and covered on the top with double iron plating one inch thick. Both ends of the vessel being sharp, it is almost impossible, at a casual glance, to tell which is the stem or which is the stern. The lower hull is one hundred and twenty-four feet long and thirty-four feet wide at the top, where it connects with the upper hull. It is six and a half feet in depth. It is sharp at both ends, the bow projecting and coming to a point at an angle of eighty degrees. It is flat-bottomed, and the sides incline at an angle of fifty-one degrees to the vertical line. It is built light of three-eighth inch iron; its average thickness being something like three quarters of an inch. It is built thus light because it is entirely protected by the impregnable upper hull. By comparing the length and breadth of the two parts of the vessel, it will be seen that the upper hull extends three feet seven inches over the sides of the lower one, and twenty-five feet over each end. The inclination of the lower hull is such that a ball cannot strike it without passing through at least a distance of twenty-five feet of water, and then striking at an acute angle of, at the most, ten degrees. It is therefore absolutely impossible that the lower hull, and for the same reasons the propeller or rudder, should be injured at all by shot. It mast strike the sides of the upper hull, where it is met by the resistance of six inches of iron and thirty inches of oak, or the turret, the defensive powers of which we shall proceed to describe. The turret, which is placed upon the deck, and which is intended as a protection to the two guns and the gunners, is an iron cylinder, .nine feet high and twenty feet internal diameter. It has two port-holes, if they may be called so, for the guns, and is intended to revolve. It is composed of plates of wrought iron, one inch thick, nine feet long, and about two feet wide, which are placed standing lengthwise, so that there are no  horizontal joints. Eight thicknesses of this plate make up the compact resistance on every side. The plates are firmly riveted together, though not so closely as to allow of no spring; and they so lap over each other that there will be only a single joint at one place. Thus the turret will be eight or nine inches thick on every side, but in addition to this Capt. Ericsson will place on the side in which the two port-holes are bored, which will of course be toward the enemy and will receive a large proportion of the enemy's shot, an additional thickness or shield of two inches of iron, so that on the fighting side the turret will present a thickness of eleven inches of wrought iron. The gunner inside a defence of this character will feel as secure as an ancient Knickerbocker in his easy-chair, while heavy balls are striking all about him, within a few feet outside, with all the force which the enemy's best guns can give them. A shell-proof flat roof of perforated plateiron, placed on forged beams inserted six inches down the cylinder, covers the top. Several sliding hatches in this give access to the turret from outside. The sides of the turret are perforated with holes of an inch diameter, to give light, and are useful, in case the battery is boarded, for musketry fire. A turned composition ring is inserted in the deck, upon which the circumference of the turret rests, but its weight is mostly upheld by a vertical shaft, ten inches in diameter, which rests firmly in a cup on a bracket attached to the main bulkhead of the vessel. A spur-wheel, six and a half inches in diameter, eleven inch face, moved by a double-cylinder engine, turns the turret around and the guns as well, directing them to any point of the compass. A rod connected with the reversing gear of the engine will enable the gunner to control the aim, so that one officer has charge of both turret and guns, and the greatest possible accuracy may be attained in firing. The armament of the vessel will consist of two Dahlgren guns of the heaviest calibre. They will be parallel, and the turning of the turret will give them their direction. The two port-holes are within about two feet of each other on the same side, and about three feet from the deck. The guns will move on forged iron slides across the turret, the carriages, which are wrought iron, being made to fit them accurately. When the gun is run in for loading, a pendulum of wrought iron will fall over the port-holes, so that no ball can enter. The guns will carry either shell or solid shot. Engineers and military men consider the eleven-inch shell, at short range, as one of the most terrific weapons introduced into practice. There is nothing that has yet been brought into practical operation that will equal them in destructive power. They will burrow under an enemy's works, and when they explode they produce an effect in the vicinity like an earthquake. The Government has also ordered for Capt. Ericsson some wrought-iron shot, very handsomely turned. The engines have been placed in the vessel for some time. They were laid two months and eight days from the time of laying the keel. They work very satisfactorily, a speed of sixty turns a minute having been already attained. The cylinders are forty inches in diameter, and twenty-two inch stroke. The boilers are on the horizontal tabular plan. One of the most important results attained in the construction of the vessel has been the entire protection of the engines, propeller, rudder, and even anchor, from shot. The propeller and rudder are both hidden under the upper hull, and the anchor is protected by the forward projecting part of the upper hull within, while it is suspended in a circular chamber, open from below, so that the men may let out or haul in the anchor quite unexposed. The ends of the vessel being sharp and of such immense force, the battery is, incidentally — for there was no stipulation that the inventor should include this advantage--one of the most powerful steam-rams that was ever built. The plate is perfectly straight on the two sides toward the end, so as to bear any shock, and the immense weight of the upper hull and deck — a weight of at least five hundred and fifty tons — would operate in one direction in the use of the vessel for this purpose. The deck being perfectly water-tight, and having no railing or bulwark of any kind, but coming flush with the top of the upper hull, admits the washing of the sea over it at liberty. The turret can also be made water-tight. The vessel will ride easily in the water, because the sea, instead of breaking against it, will pass over it as in the case of a raft. The vessel is on the principle of a life-boat, in the respect of the waterproof deck; and it is believed that it will live in a sea where a common vessel would swamp. It is expected to attain a speed with her of eight knots an hour. There have been only one hundred working days since the date of the contract for this battery. There has been only one establishment engaged in turning out the immense armor-plate, that of Abbott & Son, of Baltimore. If any other establishment could have been employed in this, the work might have been completed even sooner. The manufactory of Abbott & Son has been wholly given up to this work. Other portions of the plating have been made by Messrs. Corning, Winslow & Co., and Holdane & Co. Still the rapidity with which it has been completed shows what the country is capable of, if its energies were aroused. It is stated that the speed with which the work has been carried on would have been utterly impossible in England.
--N. Y. World, January 31.