ia 



ace may be, replaced by forces acting respectively at 

 the centre* of gravity of jjles, and proportional to 



the arena of polyhedron may be 



vd to be made up of tetrahedrons which have a com- 

 and two equal and opposite forces mar be 

 very common face, acting through the 

 of grn\ <*. face at right angle* to the face and 



proportional t he face. Hence the re<j 



result follows from the former part of this Article in 



xempliticd in Proposition I. at the end of 

 Chapter i\. 



preceding general result was first brought under the 



present writer by the late Bishop Mackenzie ; 



it was given in an examination paper in ( ionvillc and Cains 



by himself. The method by v 

 lie demonstra ill U- 2 



hy the student who is acquainted v Irostatics. 



Imagine a fluid in equilibrium acted on by no forces; 



rvMuro will be constant throu- mass. Sup- 



pose a jM.rtion of the fluid in the form of a polyhedr 

 I Decora c - briuin will not be disturbed, 



forces acting on the faces of the polyhedron will be 

 jrespe. angles to the faces ana proportional to 



ens of the faces, and will act through the centres of 

 : the faces. Hence the required result follows. 



osition may have 1 



^tated at the met 



i at Cheltenham in 1966, that he 

 been unable to in int. 



Hi <>f Art. .*! we can 'he following proj 



>: A *y*trm of ample* rtpment 



Ms fun of a pofyAtdrv* will U 

 the ajt* of Ms n*tpfa all to be 

 <* all oMttntrtb. 1 his is given by Mobius ; 

 .ige87. 



