334 Hydrostatics. 



loaded vessels, the centre of gravity has commonly been found 

 to be higher than the centre of buoyancy, by about the eighth 

 part of the extreme breadth. Accordingly, in the present in- 

 stance, the centre of gravity of the whole mass would still be 

 one foot below the surface of the water, or five feet lower than 

 the metacentre, which would be amply sufficient for the stability 

 of the ship. 



450. Such is the position of the metacentre in the vertical 

 plane at right angles to the longitudinal axis, and which reg- 

 ulates the rolling of a vessel from side to side. But there is 

 another similar point in the plane of the masts and keel, which 

 determines the pitching, or the movement of alternate rising and 

 sinking of the prow. The height of this metacentre is derived 

 from the same formula, by substituting only the length, for the 

 breadth of the vessel. Thus, let the keel measure 1 80 feet, and 

 we have 



With such a strong tendency to stability, therefore, in the direc- 

 tion of its course, a ship can scarcely ever founder in consequence 

 of pitching at sea. 



The formula now given for computing the height of the me- 

 tacentre above the centre of buoyancy, may, with some modifi- 

 cation, be deemed sufficiently accurate in practice. It is best 

 adapted, however, for cutters or frigates, and will require to be 

 somewhat diminished in the case of merchant vessels. Mr At- 

 wood performed a laborious calculation on the hull of the Cuff- 

 nells, a ship built for the service of the East India Company, 

 having divided it into 34 transverse sections, of five feet interval. 

 The result was, that the metacentre stood only 4 feet 3 inches 

 above the centre of buoyancy. But that ship, being designed 

 chiefly for burthen, appears from the drawings to have been 

 constructed after a very heavy model, its vertical sections ap- 

 proaching much nearer to rectangles than parabolas. To suit it, 

 the formula above given would have required to be reduced two 



Nl 



thirds, or to 7-^* Now the breadth of the principal section was 



