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Floating Bodies

equilibrium, centre and position

FLOATING BODIES, are those bodies which swim on the surface of a fluid, the stability, equilibrium and other circumstances of which form an interesting subject of mechanical and hydrostatical investigation, particularly as applied to the construction and management of ships and other vessels ; but as the sub ject is one involving the higher branches of calculation, and as it is difficult to obtain practical results which shall accord with those obtained from theory, on account of the difficulty of estimating the amount of the disturbing forces, our remarks must be brief and general.

The equilibrium of floating bodies is of two kinds; viz. stable or absolute, and unstable or tottering. In the one case, if the equilibrium be deranged, the body merely oscillates about its primitive position, to which it finally returns, and this is called firm or stable equilibrium ; but in the other state of equili brium, if the system be ever so little deranged, all bodies deviate more and more, and the system finally oversets and assumes a new position; and this is called unstable or tottering equilibrium. The stability of a floating hody is

greater as its centre of gravity is lower than that of the displaced fluid; it is for this reason that the ballast is put in the lower part of vessels to prevent their oversetting. The nature of the equilibrium as to stability, depends on the position of a certain point, called the meta-centre, or centre of pressure. When the meta-centre is lower than the centre of gravity, the equilibrium is tottering ; when the meta-centre coincides with the centre of gravity, the body will remain at rest in any position it is placed in ; when the meta-centre is above the centre of gravity, the body will always have a tendency to recover its original position, and the equilibrium will be stable.