In the design of a vessel the first consideration is to obtain sufficient buoyancy, the second is to obtain stability.

Let G be the centre of gravity of the vessel, H the centre of gravity of displaced fluid when floating normally. If the vessel is given a small displacement let H1 = centre of gravity of the displaced fluid in the new position. Draw a vertical through H1 cutting G H in M. Then M is the meta centre.

If M is above G the vertical pressure of the displaced fluid introduces a couple tending to restore the vessel to its original position.

One of the most important problems in Naval architecture is to secure the ascendancy under all circumstances of the meta centre over the centre of gravity.