NOTES

TO THE

SKETCH OF EXPEDIENTS.

Swimming.-Erroneous conclusions respecting the bucyancy of the human body result from overlooking the particular figure of individuals. While one person can scarcely sustain himself afloat, a considerable weight will prove necessary to sink another confiding in the natural properties of his structure.

Life-Preservers.-These are by no means recent inventions, as we are told of one contrived by the Chevalier de Lanquer in 1675, which could be contained in the pocket. This has been supposed to consist of some kind of habit susceptible of inflation. Its effect was exhibited to Louis XIV. in 1695, and the inventor obtained a patent for its construction.

When land-troops are on board of a vessel in danger of wreck, it is recommended that each man shall secure his canteen on his breast with the same strap by which it is usually affixed at his side. Lying on his back in the water, its buoyancy will bear him up, for the canteen is somewhat larger than what would be required merely to preserve a person from sinking.

The Cork-Jacket seems to have originally been called the Cork-Waistcoat, and to have appeared almost, if not exactly, in the shape of what is now denominated the Seaman's Friend: which latter consists either of two or four pieces of cork. Without controverting Dr Wilkinson's claim to be admitted the first exhibiter in Britain, it may here be ob

served that, in 1758, a M Dubourg of London adopted a similar expedient. This is described as composed "of four pieces of cork, two for the breasts and two for the back, each pretty near in length and breadth to the quarters of a waistcoat without flaps, the whole covered with coarse canvas, with two holes to put the arms through. There is a space left between the two back-pieces, and the same between each back and breast-piece, that they may fit the easier to the body." But Dr Wilkinson had previously read a memoir on the subject at a meeting of the Society for Encouragement of Arts. However, it ought not to be omitted that, in 1741, John Frederic Bachstrom, a German, proposed a life-preserver of cork, consisting of two pieces for the back and two for the breast, together with smaller portions to fix under the arms and to the shoulders. The cork, if appropriated to soldiers, he says, should be in one entire piece on the back and breast, the better to resist a musket-ball; but if used by seamen, it should be divided into small portions to enable them to go through their manoeuvres with facility. Bachstrom, however, goes much farther, for he proposes by five pounds of cork fixed to the fore-part of the saddle, and as much behind, to float a squadron of horse through a river in safety, while the riders are accoutred with their own proper apparatus.

Other applications of cork, strictly in the form of jackets, by foreigners, might be quoted, such as one by M. Bonal of Dieppe, and another by Signor Gelaci, which latter was constructed so, that the pieces employed should always float horizontally. Likewise the scaphandre of the Abbe de la Chapelle, consisting of several rows of small square pieces of cork; and the Count de Puysegur's cork gudle, which was eight inches broad, six thick, and weighed 13 pounds. It was loaded with three pounds of lead to preserve it against an improper position from accident.

Above a century ago, M. Ozanam proposed, as a security against shipwreck, to have a girdle composed of two flat hollow semicircular bodies, whereby a person would always be supported above water. The substance of these bodies he considers immaterial, provided they be light, and of sufficient strength to resist the pressure of the waves.

It evidently appears that Mr Daniel's life-preserver, de scribed page 466, on which he declares he expended

510

PRESERVATION OF MARINERS.

£1500, and which has been so well rewarded, is only a revival of one that appeared nearly at the same time as the cork waistcoat or jacket in 1758. It was then described as 66 a kind of double belt wore immediately below the arm-pits, of the same kind of leather with that of the bagpipe, to one end of which a pipe is fixed, pointing to the mouth so as easily to blow the belt full of air when necessary, which will keep the body buoyant." It is earnestly to be desired that both Parliament and Public Societies, before bestowing pecuniary and honorary distinctions on individuals, would strictly ascertain how far they are merited. How can we gravely listen to a deliberate investigation by the National Council of the Empire, of whether cork will assist people to swim!!

Life-Boat. Mr Lukin seems to have been completely aware of two indispensable principles in the construction of a life-boat. 1. To give so much buoyancy to the upper part as to render the specific gravity of the whole vessel and its lading less than the specific gravity of the water which it shall displace. 2. To load the keel below with weight sufcient to preserve the boat upright, or to give it the power of regaining its proper position when thrown out of it.

The former he practically obtained by adding a projecting gunwale of cork, and forming a hollow inclosure within the boat, containing so much air as necessary for completing the buoyancy; and the latter was accomplished by bolting a false keel of cast iron under the common keel. Instead of the projecting gunwales of cork, he likewise made an experiment, by fitting up a boat with an internal lining of that substance; whence it appears, that although he did construct a serviceable life-boat, its principles were essentially different from those adopted by Mr Greathead. Mr Wilson afterwards put the principle suggested by him, of obtaining buoyancy by empty gunwales, in execution.

It has confidently been maintained, that Mr Greathead is not the actual inventor of the boat, which passes under his name, and that the real merit is due to William Wouldhave, a painter in South Shields. The model of a boat cased with cork, and of the flat or flaunching form, is said to have been presented to the South Shields Committee by him, and that Mr Greathead was employed to build a boat after it, in

which he introduced the curved keel, according to a model which he had himself exhibited. If these facts be true, they may justly be the subject of national reproach. It is also maintained, that curvature in the keel of a life-boat is a radical error in construction, and that every vessel is thereby rendered more liable to overset.

Communications with the shore.-Since the preceding sketch was completed, a publication by Captain Manby, on the means adopted by him for preserving shipwrecked mariners, has appeared. There his whole system is concisely and perspicuously laid down, and embraces all that detail which is only glanced at here. A perusal of his useful work, which affords a valuable acquisition to the expedients for mitigating the dangers of shipwreck, cannot but be deemed interesting.

Captain Manby, in the course of his treatise, complains of frequent insinuations that he is not the inventor of the methods adopted of conveying lines from projectiles. The author of the preceding sketch had nothing more in view than to connect a few notes and observations on the subject in general, and he now regrets that he has not entered into a more minute investigation concerning the successive periods of the inventions or devices which have been exhibited. He is well aware that the merit due to one is sometimes given to another, that real desert is too often overlooked, and unless it were possible to restrain the imagination of mankind, that the vindication of inventions is no easy task. Yet in this particular instance, he cannot disguise his opinion, that all the four expedients above described, of which Captain Manby's is the latest, rest on principles essentially and virtually the same.