136 Prof. A. M°Aulay on Spontaneous Generation 



be the general nature of those freely mobile electrons ? The 

 answer is almost axiomatic. The free gether is a stable form 

 of the solid. By finite straining (we suppose below by finite 

 small straining) the stability is left behind. There is a second 

 state, providing for electrons, which may or may not be 

 associated with a second absolute minimum value of the 

 volume potential energy. There is a critical condition such 

 that if the strains in an assigned manner exceed it, the 

 medium instead of tending to return to the free aether state 

 tends to deviate still further ; and though this critical con- 

 dition is not one of absolute instability, we may refer to it as 

 the unstable state. 



The accompanying diagram, though an imperfect repre- 

 sentation of wasa function of e, f, g, much aids the com- 

 prehension of what we have now to say. There are two 



