Harper's New Monthly Magazine, Vol. 3, July, 1851. Various
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In case of these life-cars, therefore, arrangements are made for sending the hawser out from the shore to the ship. The apparatus by which this is accomplished consists, first, of a piece of ordnance called a mortar, made large enough to throw a shot of about six inches in diameter; secondly, the shot itself, which has a small iron staple set in it; thirdly, a long line, one end of which is to be attached to the staple in the shot, when the shot is thrown; and, fourthly, a rack of a peculiar construction to serve as a reel for winding the line upon. This rack consists of a small square frame, having rows of pegs inserted along the ends and sides of it. The line is wound upon these pegs in such a manner, that as the shot is projected through the air, drawing the line with it, the pegs deliver the line as fast as it is required by the progress of the shot, and that with the least possible friction. Thus the advance of the shot is unimpeded. The mortar from which the shot is fired, is aimed in such a manner as to throw the missile over and beyond the ship, and thus when it falls into the water, the line attached to it comes down across the deck of the ship, and is seized by the passengers and crew.
Sometimes, in consequence of the darkness of the night, the violence of the wind, and perhaps of the agitations and confusion of the scene, the first and even the second trial may not be successful in throwing the line across the wreck. The object is, however, generally attained on the second or third attempt, and then the end of the hawser is drawn out to the wreck by means of the small line which the shot had carried; and being made fast and "drawn taut," the bridge is complete on which the car is to traverse to and fro.
The visitors at Long Branch, a celebrated watering place on the New Jersey coast, near New York, had an opportunity to witness a trial of this apparatus at the station there, during the last summer: a trial made, not in a case of storm and shipwreck, but on a pleasant summer afternoon, and for the purpose of testing the apparatus, and for practice in the use of it. A large company assembled on the bank to witness the experiments. A boat was stationed on the calm surface of the sea, half a mile from the shore, to represent the wreck. The ball was thrown, the line fell across the boat, the car was drawn out, and then certain amateur performers, representing wrecked and perishing men, were put into the car and drawn safely through the gentle evening surf to the shore.
FIRING THE SHOT.
A case occurred a little more than a year ago on the Jersey shore not very far from Long Branch, in which this apparatus was used in serious earnest. It was in the middle of January and during a severe snow storm. The ship Ayrshire, with about two hundred passengers, had been driven upon the shore by the storm, and lay there stranded, the sea beating over her, and a surf so heavy rolling in, as made it impossible for any boat to reach her. It happened that one of the stations which we have described was near. The people on the shore assembled and brought out the apparatus. They fired the shot, taking aim so well that the line fell directly across the wreck. It was caught by the crew on board and the hawser was hauled off. The car was then attached, and in a short time, every one of the two hundred passengers, men, women, children, and even infants in their mothers' arms, were brought safely through the foaming surges, and landed at the station. The car which performed this service was considered as thenceforth fully entitled to an honorable discharge from active duty, and it now rests, in retirement and repose, though unconscious of its honors, in the Metallic Life-Boat Factory of Mr. Francis, at the Novelty Iron Works.
In many cases of distress and disaster befalling ships on the coast, it is not necessary to use the car, the state of the sea being such that it is possible to go out in a boat, to furnish the necessary succor. The boats, however, which are destined to this service must be of a peculiar construction, for no ordinary boat can live a moment in the surf which rolls in, in storms, upon shelving or rocky shores. A great many different modes have been adopted for the construction of surf-boats, each liable to its own peculiar objections. The principle on which Mr. Francis relies in his life and surf boats, is to give them an extreme lightness and buoyancy, so as to keep them always upon the top of the sea. Formerly it was expected that a boat in such a service, must necessarily take in great quantities of water, and the object of all the contrivances for securing its safety, was to expel the water after it was admitted. In the plan now adopted the design is to exclude the water altogether, by making the structure so light and forming it on such a model that it shall always rise above the wave, and thus glide safely over it. This result is obtained partly by means of the model of the boat, and partly by the lightness of the material of which it is composed. The reader may perhaps be surprised to hear, after this, that the material is iron.
Iron—or copper, which in this respect possesses the same properties as iron—though absolutely heavier than wood, is, in fact, much lighter as a material for the construction of receptacles of all kinds, on account of its great strength and tenacity, which allows of its being used in plates so thin that the quantity of the material employed is diminished much more than the specific gravity is increased by using the metal. There has been, however, hitherto a great practical difficulty in the way of using iron for such a purpose, namely that of giving to these metal plates a sufficient stiffness. A sheet of tin, for example, though stronger than a board, that is, requiring a greater force to break or rapture it, is still very flexible, while the board is stiff. In other words, in the case of a thin plate of metal, the parts yield readily to any slight force, so far as to bend under the pressure, but it requires a very great force to separate them entirely; whereas in the case of wood, the slight force is at first resisted, but on a moderate increase of it, the structure breaks down altogether. The great thing to be desired therefore in a material for the construction of boats is to secure the stiffness of wood in conjunction with the thinness and tenacity of iron. This object is attained in the manufacture of Mr. Francis's boats by plaiting or corrugating the sheets of metal of which the sides of the boat are to be made. A familiar illustration of the principle on which this stiffening is effected is furnished by the common table waiter, which is made, usually, of a thin plate of tinned iron, stiffened by being turned up at the edges all around—the upturned part serving also at the same time the purpose of forming a margin.
The plaitings or corrugations of the metal in these iron boats pass along the sheets, in lines, instead of being, as in the case of the waiter, confined to the margin. The lines which they form can be seen in the drawing of the surf-boat, given on a subsequent page. The idea of thus corrugating or plaiting the metal was a very simple one; the main difficulty in the invention came, after getting the idea, in devising the ways and means by which such a corrugation could be made. It is a curious circumstance in the history of modern inventions that it often requires much more ingenuity and effort to contrive a way to make the article when invented, than it did to invent the article itself. It was, for instance, much easier, doubtless, to invent pins, than to invent the machinery for making pins.
The machine for making the corrugations in the sides of these metallic boats consists of a hydraulic press and a set of enormous dies. These dies are grooved to fit each other, and shut together; and the plate of iron which is to be corrugated being placed between them, is pressed into the requisite form, with all the force of the hydraulic piston—the greatest force, altogether, that is ever employed in the service of man.
THE HYDRAULIC PRESS.
The machinery referred to will be easily understood by the above engraving. On the left are the pumps, worked, as represented in the engraving, by two men, though four or more are often required. By alternately raising and depressing the break or handle, they work two small but very solid pistons which play within cylinders of corresponding bore, in the manner of any common forcing pump.
By means of these pistons the water is driven, in small quantities but with prodigious force, along through the horizontal tube seen passing across, in the middle of the picture, from the forcing-pump to the great cylinders on the right hand. Here the water presses upward upon the under surfaces of pistons working within the great cylinders, with a force proportioned to the ratio of the area of those pistons compared with that of one of the pistons in the pump. Now the piston in the force-pump is about one inch in diameter. Those in the great cylinders are about twelve inches in diameter, and as there are four of the great cylinders