See that article, and SHIPBUILDING (Encyc.), and likewise FLOATING Bodies (Suppl.). In the Transactions of the Royal Society of London for 1798, Mr Atwood has completed his disquisition on the Stability of Ships; but as the memoir cannot be abridged, we must refer the scientific naval architect to the original for much useful information.
A small work has lately been published by Charles Gore, Esq.; of Weimar in Saxony, upon the Reflective Velocity of Floating Bodies varying in Form. It contains merely the results of two series of experiments; from the first of which series, it seems to appear that the form best calculated for velocity is a long parallel body, terminating at each end in a parabolic cuneus, and having the extreme breadth in the centre. Also, that making the cuneus more obtuse than is necessary to break with fairness the curve line into the straight, creates a considerable degree of impediment. And Mr Gore is inclined to think, that the length of ships, which has already been extended with success, to four times the breadth, is capable, with advantage, of still further extension, perhaps to five, and, in some cases, even to six times.
The second set of experiments was instituted to ascertain the respective degrees of stability, or power of resisting the pressure of the wind, in carrying sail, on bodies of different forms. The bodies used in the experiments had their specific capacities and weights precisely equal, but their forms different; and from the results, it appears that the form of a midship body, best adapted for stability only, is a flat bottom, with perpendicular sides; and that the next best adapted is a semicircle. But as there exists much difficulty in constructing the former with sufficient strength, besides its being ill adapted to heavy seas, as, by the sudden descent in pitching, the bottom will strike the water nearly at right angles, and sustain thereby a tremendous shock. And as the latter seems to be too inclinable to transverse oscillation, or rolling, and also to be deficient in capacity for many services, our author is of opinion, that a midship body, of a compounded form, is most applicable to general purposes.
On account of the few documents before us, we are unable to speak critically concerning this tract. To benefit naval architecture, we are of opinion, that the method of experiment is more forcible and expeditious than that of calculation; yet conclusions from experiments must be drawn with great caution. It is by no means certain that a result obtained for a body of a given bulk will obtain for similar bodies which differ in dimensions.
We shall conclude this short article with a statement of the principles upon which Patrick Miller, Esq.; of Dallington (Scotland), proposes to construct ships and vessels which cannot founder.
The vessel is to be kept afloat, without the aid of its sides, solely by the buoyancy of its bottom, which is flat; the bottom never being so deeply immersed as to bring the upper surface thereof on a level with the water; such vessels not being constructed for the purpose of carrying cargoes, but for that of carrying passengers, with the necessary stores and provisions; and as these vessels are not kept afloat by the aid of their sides, but by the buoyancy of their bottom, as above described, they cannot sink, and therefore pumps are not required; nor are they in any respect necessary for the preservation of such vessels. The said vessel is put in motion, during calms, and against light winds, by means of wheels. These wheels project beyond the sides of the vessel, and are wrought by means of capstans; the number and the dimensions of the wheels depend upon the length of the vessel. These wheels are built with eight arms, which consist entirely of plank. Sliders are used to work and to keep the vessel to windward when under sail. These sliders are placed in the centre of the vessel, from stem to stern; they are made of plank, and the number and dimensions must depend on the length of the vessel; and they are raised and let down, down, either by the hand, or by means of a purchase, according to the size of the vessel. Vessels of this construction draw water, in proportion to their dimensions, as follows: a vessel of forty feet in length, and from thirteen to nineteen feet in breadth, will draw from fifteen to sixteen inches of water. One of fifty feet in length, and from seventeen to twenty-four feet in breadth, will draw from fifteen to eighteen inches of water. One sixty feet long, and from twenty to twenty-eight feet broad, will draw from eighteen to twenty-one inches of water. One seventy feet long, and from twenty-three to thirty-two feet broad, will draw from twenty-one to twenty-four inches of water. One eighty feet long, and from twenty-seven to thirty-seven feet broad, will draw from twenty-four to twenty-seven inches of water. One ninety feet long, and from thirty to forty-two feet broad, will draw from twenty-seven to thirty inches of water. One of one hundred feet in length, and from thirty-three to forty-seven feet in breadth, will draw from thirty to thirty-three inches of water.
As, from the principle upon which this vessel is constructed, she cannot sink, the invention must prove a means of saving many lives; and as it will give more room and height between the decks than any vessel of the same dimensions of another construction, it must add greatly to the comfort and accommodation of persons at sea of all descriptions. It is expected that, from these advantages, a more general and friendly intercourse amongst nations will take place, which will have the effect to diffuse knowledge, and to remove national prejudices, thereby promoting the general welfare of mankind. At present (says Mr. Miller), it would be altogether improper to give any description of ships of greater dimensions, lest it should be converted to a purpose very different from that intended by the inventor.