86 REVIEW. 



the meiacenlrc, it is absolutely necessary that the moment of the 

 weight above that point, be equal to the moment of the weight 

 below the same point. For if those moments are not equal, some 

 force, proportionate to their difference, will be required to act at 

 a distance from the axis, to make the body revolve." 



This observation is so palpably at variance with that quoted 

 before, and both so evidently erroneous, as to require but little 

 comment. And as Capt. P. observes, " the experiments clearly 

 prove, that when the moment of the weight above the metacentre, 

 is equal to the moment of the weight below the metacentre, the 

 body does not possess the power of resisting motion : conse- 

 quently, any force, acting at a distance from the metacentre 

 will destroy the equilibrium, and make the body revolve sofreclif, 

 that it will instantly upset ; therefore, and in order that the body 

 may not revolve too freely, it is absolutely necessary that the 

 moment of the weight below the metacentre, be equal to the mo- 

 ment of the weight above the metacentre, plus the moment of 

 the inclining force ; and, as the inclining power becomes greater, 

 and increases the angle of inclination, the sine of the angle be- 

 comes greater also, and increases the force of stability ; and 

 consequently, the moment of stability, which is equal to the 

 difference betwee^ the moment of the weight below the metacentre 

 and the moment of the weight atove that point, Ls always equal 

 to the moment of the inclining force : and the progressive increase 

 of stability, prevents the body from revolving too freely ^^ 



In the fourth paper it is shewn by various illustrations, how 

 stability is produced, with respect to form generating that pro- 

 perty : and it is clearly explained how great stability, and a 

 comparatively small direct resistance may be at once obtained. 

 But, it is observed, that, altlKDUgh science clearly explains the 

 means by which those properties may be obtained, it does not 

 mark the limits to which they may be extended, without in- 

 juriously effecting other necessary qualities; and, that, to obtain 

 such essential knowledge, it is absolutely necessary to make ex- 

 periments with ships at sea. 



The fifth and last paper is on the " inertia" of bodies ; and 

 on the "momentum" of bodies. And here again Capt. P. 

 clearly proves Mr. Ilenwood to have fallen into a most serious 

 error. That gentleman has positively asserted, that if the weights 

 in the fore and after bodies of a ship are equal, and the centres of 

 gravity of those weights equally distant from the centre of gravity 

 of the whole, the forces with which those weights will act in 



