A KINETIC THEORY OF MATTER. 237 



sequent motion will be the same in the two cases. 

 If in the one case the springs are made more 

 and more stiff, and in the other case the angular 

 velocities of the fly-wheels are made greater and 

 greater, the periods of the vibrational constituents 

 of the motion will become shorter and shorter, 

 and the amplitudes smaller and smaller, and 

 the motions will approach more and more nearly 

 those of two perfectly rigid groups of material 

 points moving through space and rotating 

 according to the well-known mode of rotation 

 of a rigid body having unequal moments of 

 inertia about its three principal axes. In one 

 case the ideal nearly rigid connection between 

 the particles is produced by massless exceedingly 

 stiff springs ; in the other case it is produced 

 by the exceedingly rapid rotation of the fly- 

 wheels in a system which, when the fly-wheels 

 are deprived of their rotation, is perfectly limp. 



The drawings (Figs. 44 and 45) before you 

 llustrate two such material systems. 1 The 



In Fig. 44 the two hooked rods seen projecting from the sphere 

 are connected by an elastic coach spring. In Fig. 45 the hooked rods 



