10. In a parabola edge-Avars suspended iy the vertex, D ~ axis -f- 



parameter. 



To find the centre of oscillation practically, suspend the body freely 

 by the point of suspension, and make it vibrate in small arcs, counting 

 the vibrations it makes in any given time, as one minute. Call the num- 

 ber in a minute ??, then will the distance of the centre of oscillation be 



^- inches. For a still more accurate method see Captain Kater'a 

 Paper in the Phil. Trans, for 1818. 



CENTRE of Percussion. 



When the percutient body revolves about a fixed point, the centre of 

 percussion is the same as the centre of oscillation. But when the body 

 moves with a parallel motion, the centre of percussion is the same as the 

 i ontre of gravity. 



CENTRE of Pressure. 



Centre of pressure of a fluid against a plane, is that point against which 

 a force being applied equal and contrary to the whole pressure, it will 

 sustain it, so as that the body pressed on will not incline to either side. 

 This, according to some writers, is the same as the centre of percussion, 

 supposing the axis of suspension to be at the intersection of this plane 

 with the surface of the fluid j while others assert, that though the dis- 

 tance of this intersection from the centre of pressure is the same as that 

 of the centre of percussion, yet that they do not in general lie in the same 

 line, and consequently are not the same point. The centre of pressure 

 upon any plane parallel to the horizon, or upon any plane where the 

 pressure is uniform, is the same as the centre of gravity of that plane. 



CENTRIFUGAL Force. See Central Forces. 

 CENTRIPETAL Force. See Central Forces. 



CERES. 



This planet was discovered by M. Piazzi, of Palermo, Jan. 1, 1801. For 

 its elements, &c see Planets, elements of. 



CHANCES, doctrine of.( Wood.) 



1. If an event may take place in n different ways, and each of these be 

 equally likely to happen, the probability that it will take place in a speci- 

 fied way is , certainty being represented by unity. 



