CHAPTER XIV. 



OF THE CENTRE OF PRESSURE. 



506. THE subject of the present chapter might have been placed in 

 juxtaposition with the doctrine of pressure on plane surfaces ; but we 

 chose to reserve it for the conclusion of fluid equilibrium, and in as 

 brief a manner as possible we shall now view the centre of pressure, 

 by illustrating a few select examples dependent upon its principles. 



The Centre of Pressure of a plane surface immersed in a fluid, or 

 sustaining a fluid pressing against it, is that point, to which, if a force 

 be applied equal and contrary to the whole pressure exerted by the 

 fluid, the plane will remain at rest, having no tendency to incline to 

 either side. 



It is manifest from this definition, that if a plane surface immersed 

 in a fluid, or otherwise exposed to its influence, be parallel to the 

 horizon ; then, the centre of pressure and the centre of gravity occur 

 in the same point, and the same is true with respect to every plane on 

 which the pressure is uniform; but when the plane on which the 

 pressure is exerted, is any how inclined to the horizon, or to the 

 surface of the fluid whose pressure it sustains ; then, in order to 

 determine the centre of pressure, we must have recourse to the 

 resolution of the following problem. 



PROBLEM LXIII. 



507. Having given the dimensions and position of a plane sur- 

 face immersed in a fluid, or otherwise exposed to its influence : 



It is required to determine the position of the centre of 

 pressure, or that point, to which, if a force be applied equal 

 and opposite to the pressure of the fluid, the plane shall 

 remain in a state of quiescence, having no tendency to incline 

 to either side. 



