THE INDUSTRY OF AJLJL, NATIONS.

There is also a model of a steamship proposed by Darius Davidson, whichdemands attention, on account of the magnitude of its dimensions. The lengthof keel is 700 feet, and of deck 500 feet; beam 80 feet, and depth 60 feet. Itis to be propelled by sixteen engines, indicated in the model by eight sets of smokepipes placed along the deck; and her time in crossing the Atlantic, it is antici-pated by the sanguine Mr. Davidson, will be inside of five days. The pointedends, projecting 100 feet from the body of the hull, would make capital adjunctsto a machine for diving purposes. A false bow, similar to the above, was triedon the steamboat Albany, in 1838, and discarded.

William A. Sillen exhibits a good model of a ship, to which he has attached acard, stating that having discovered a diversity of opinions as to the proper shapefor insuring the desired sea-going qualities in a ship, he concluded there was somemistake in the ordinary theory, and was led to institute a series of peculiar exper-iments, by which (mirdbile dictu ) he was convinced that the water does not passalong the ship’s sides and bottom in lines parallel to the surface. Diagonals, orproving lines, have been employed in laying down a ship’s lines ever since draw-ings were used in their construction.

Proposed plan for a yacht Petrel, by P. S. Copley. At the load water-linethis vessel will possess no stability, and the motion easily induced will abruptlycease on the immersion of the broad, flaring side to leeward. Place her in aninclined position, and the motion of the water upward and backward, passingunder its surface around the angles and irregularities, will be very varied, and, asmay be readily conceived, not particularly conducive to speed. The double keelwill not oppose twice the resistance of a single one to leeway, but will offer itsfull proportion of friction. A keel, at any rate, is of no use in running with afree wind, and when on the wind a centre-board will answer the purpose equallywell, and may be raised or lowered to suit the varying requirements. Smallvessels may be made as strong without them, and the handling of the weight,with the assistance of counterbalance springs, as applied in the yacht Maria, is avery simple matter. The U. S. Schooner Onkaliye had a section similar to thatof the “ Petre,” (with the exception of the double keel),, and was indebted to it forconstantly endangering her spars and ultimate loss by capsizing.

The French department of the Exhibition contains a model of a steamer pro-pelled by submerged wheels, precisely similar to those known in this country asHunter’s patent. A pair of ordinary radial wheels are placed horizontally in thevessel below the water-line, with the paddles projecting from the sides. Restrict-ed as they necessarily are in size, an engineer would at once anticipate an enor-mous slip, amounting, in the applications of this plan, made by the United StatesGovernment, to about fifty per cent. Even to the most unprofessional, one wouldthink this proposition of carrying wheels and wheel houses (the latter, moreover,filled with water) inside the hold of the vessel, would be preposterous.

LIFE-BOATS.

I N consequence of the exertions of the National Shipwreck Institution of GreatBritain, much attention has there been devoted to the subject of life-boats; anda collection of the best, comprising no less than fifty-four specimens selected andcontributed by the Duke of Northumberland, the President of the Institu-tion, formed one of the prominent features of the London Exhibition. Theencouragement of these valuable productions, furnished by the private munificenceof the distinguished President, was so splendid an example of liberality in thecause of humanity and practical science, that the jury having cognizance of thesubject, reported him worthy of a Council Medal. The importance of the subjectwill be recognized without a statistical exhibit here of the numerous shipwrecksand frightful loss of life, which it is too frequently the duty of the daily journalsto record. The Steamboat Law, passed by Act of Congress, on the 30th of August1852, provides that every steamer shall carry a number of life-boats, proportionateto her size, amounting in the case of a vessel exceeding fifteen hundred tons tosix; and a number of life preservers otherwise specified.

Besides the buoyancy requisite to carry a heavy load of passengers with itscrew, a life-boat should be formed to pull easily and be readily managed, and inthe event of being upset, should be able to right itself. A sad experience hasshown in more than one instance that the want of this last quality may occasionthe loss of a brave crew. The form best adapted for the purposes of a boat to bechiefly employed under the exigencies of a storm in which ordinary boats areunable to live, is that usually given to whale-boats, but with more breadth ofbeam to furnish the stability required by the incautious movements of frightenedpassengers, and the necessity for rescuing them from the water and dragging themin over the gunwale. That this valuable property may, however, be carried toexcess, seems to be demonstrated by several recorded instances of life-boats havinga proportion of beam, exceeding one-third of the length, in conjunction probably

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with full terminations, being turned end over end in a heavy sea. To enable a boatto right itself when upset, it should be ballasted along the bottom, and have air-tanks at the ends carried up as high as practicable by sheer of gunwale. Waterballasting to be admitted at pleasure, has been used in a tank extending along thekeel; and although the attainable variation in weight of ballast is useful whenunder sail, at which time, however, the unemployed men may sit to windwardand answer the same purpose, yet, in more ordinary circumstances, and par-ticularly at the moment of launching, when accidents are very likely to occur,the advantages of permanent ballast are superior to those attendant on thatwhich can only be taken in when the boat is afloat, and the chief merit of whichlies in the diminished weight for transportation ashore. Probably the best man-ner of ballasting a boat is to give the bottom an inner lining of common cork,covered by an ordinary flat floor; thus reducing the internal capacity andenabling it to rise when swamped under a sea, and still sufficiently heavy to insurestability. With the buoyancy occasioned by the use of air-tanks, a boat heavilyladen and filled with water may be able to swim, and, indeed, rise a few inchesabove the surface of the water: now, if in this latter case, there was an outlet orhole in the bottom of the boat, the water inside and outside would endeavor toreach a common level, and that inside would run out, and the boat being lightened,would continue to rise until the general buoyancy and weight corresponded—self-acting valves opening outwards, therefore, are valuable adjuncts to a life-boat.

The Act of Congress, which has been referred to, specifies that the life-boatsmust be made of metal. Where a wooden boat would be crushed amid thefragments of a wreck, or stove by a projecting rock, a metal one will escape withan indentation which may be easily repaired, and at any rate interferes but littlewith its useful properties. In the case of fire they are pre-eminently superior.Their tightness, freedom from worms, and immunity from warping by exposureto the sun, has occasioned the employment of metal as the chief material of con-struction, to be regarded as one of the prime elements of a life-boat. A woodenWhitehall boat, built and exhibited by one of the best builders in New-York,illustrates the superiority of metal as a material. During the short time whichhas elapsed since it was placed in the Exhibition, the dryness of the atmospherehas already sprung several of the planks and fastenings and opened some of theseams.

Francis' Life-Boat .—It is to be regretted that the owners of Francis’ patent,who have manufactured over twenty-five hundred metallic boats, have not ex-hibited a fair specimen of their life-boats—considering the term in its definitemeaning and per se. The one furnished is a copper, man-of-war-cutter, thirty-onefeet long, of the ordinary model, and furnished with air-tanks at the ends. Thechief, and most valuable pecu-liarity is the corrugations ofthe metal, resembling external-ly a clinker-built boat, and ma-terially enhancing the strengthwith but little addition to theweight. The sheets of whichthe boat is formed, are struck

into shape between dies operated by a hydraulic press, and the variations fromthe original plane superfices are chiefly taken up by the corrugations. The greatincrease of strength is exemplified by the exhibition of examples of similar sheets,in which the corrugated one supports a heavy load without appreciable flexure,and the other and plain one sinks under its own weight. Galvanized iron ischeaper, but slightly inferior to copper, and is more generally used.

In storms of such violence, that it is impossible to manage a boat, communi-cation may be instituted betweenthe shore and a wreck, by meansof a hawser drifted ashore by abarrel, or thrown from the shorewith the assistance of a rocket ora ball. On this hawser a closecar, conveying passengers, repre-sented in the accompanying draw-ing, may be traversed backward and forward by the lines attached to its ends.

Lewis Raymond , of Ffew- York , furnishes a galvanized iron life-boat, of thewhale-boat model, with air-tanks at the ends and along the sides, and fittedwith self-acting bailing valves, the uses and advantages of which have beenadverted to.

In the English department is exhibited a model of an iron boat, or car, withno name attached. It has no rowlocks or thole pins, and is shaped like a carwithout a top. Its distinguishing peculiarity is an arrangement of buoyant fen-ders placed on each side, about the width of the boat distant from it, and nearlyequal to its length—they are placed on a flexible beam fastened to stanchionsextending to the boat, the centre one of which is stationary, and the end onesallowed to slip into recesses or cases built in the boat and extending under itsseats.