REVIEW. 85 



have a clear demonstration, that, in resisting and reproducing 

 motion, the weight of a body when seated in the water, acts in 

 precisely the same manner as when the body is suspended out of 

 the water. 



It is proved again, by this experiment, that the centre of gravity 

 of a ship cannot be the point through which the axis of rotation 

 passes, because that point is not the centre of gravity of the whole 

 system, neither when the body is inclined in the water, nor when 

 it is suspended and inclined out of the water. 



The axis of rotation must pass through that point which is the 

 centre of gravity of all the various forces which act on a ship. 

 But, when a ship is inclined, its centre of gravity is not in the 

 same vertical as the mean direction of the supporting power of 

 the water — that vertical in which the centre of gravity of the 

 various efforts of the water is situated ; - therefore, the centre of 

 gravity of the ship cannot be the centre of gravity of the down- 

 ward vertical pressure in an inclined position ; and, consequently, 

 it cannot be the centre of gravity of the whole system. And, as 

 Capt. P. shews, it is not the weight of the ship alone which de- 

 termines the amount of the downward vertical pressure, but the 

 combined efforts of the weight of the ship and the inclining force ; 

 and the centre of gravity of those efforts must be in the same ver- 

 tical as the mean direction of the supporting power of the water ; 

 and, therefore, as the centre of gravity of all the various forces is 

 in that vertical, the axis of rotation, or the point round which the 

 forces are ballanced, must necessarily be in the same vertical also. 



At page 5Qy Capt. P. quotes an observation of Mr. H.'s, in 

 which it is asserted that, " if the axis of rotation pass through 

 the metacentre, the ship can have no force of stability ; ^nd con- 

 sequently, that the smallest impulse of wind, acting to incline the 

 ship, must inevitably overset her." But Capt. P. has proved by 

 the experiment last alluded to, that a ship must possess stability 

 as long as its centre of gravity is situated below the metacentre ; 

 and, that when the model is seated in the water, and when sus- 

 pended out of it, the stability progressively diminishes, as the 

 centre of gravity is made to approach the point which experiment 

 in the water determines to be the place of the metacentre ; and 

 through which point the axle passes that suspends the model 

 out of the water. 



Again, at page 57, Capt. P. quotes another observation of Mr. 

 H.'s, namely: " In order that the ship may revolve freely, that 

 is, with perfect facility either way, round an axis passing through 



