A KINETIC THEORY OF MATTER. 245 



the resultant of the motion it would have in 

 virtue of the circulation alone, were the solid 

 at rest, and the motion it would have in virtue 

 of the motion of the solid itself, had there been 

 no circulation established through the aperture. It 

 is interesting and important to remark in passing 

 that the whole kinetic energy of the liquid is the 

 sum of the kinetic energies which it would -have in 

 the two cases separately. Now, imagine the whole 

 liquid to be enclosed in an infinitely large rigid 

 containing vessel, and in the liquid, at an infinite 

 distance from any part of the containing vessel, 

 let two perforated solids, with irrotational 

 circulation through each, be placed at rest near 

 one another. The resultant fluid motion due to 

 the two circulations will give rise to fluid pressure 

 on the two bodies, which if unbalanced will 

 cause them to move. The force systems force - 

 and-torques, or pairs of forces required to 

 prevent them from moving will be mutual and 

 opposite, and will be the same as, but opposite 

 in direction to, the mutual force systems required 

 to hold at rest two electromagnets fulfilling the 



