EQUILIBRIA AND THEIR DISPLACEMENT 267 



nomenon the development of muscle by exercise is a 

 familiar illustration. We might, therefore, look upon 

 the principle of Le Chatelier as an extension to in- 

 animate substances of the faculty of accommodation. 



We may also express the principle by saying that 

 every system, chemical or physical, which is in equi- 

 librium is conservative, that is, tends to remain un- 

 changed. In the world about us, however, changes 

 are constantly occurring in the molecular systems. 

 We conclude, therefore, that they are not in equilib- 

 rium. Certain transformations are taking place in 

 these systems naturally, that is, without external cause. 

 Such a system, for example, is the solar system, in which 

 we live, where the transformations take place "of 

 themselves, " as we might say. 



What are the typical transformations which take 

 place naturally? We have progressed far enough hi 

 our study to realize that the production of molecular 

 motions, or "heat," at the expense of work is a natural 

 process, as in the phenomenon of friction. Similarly 

 the mixing of gases by diffusion is a natural process. 

 The transfer of energy from molecules with high kinetic 

 energy to those of low is also natural, that is, the transfer 

 of heat from a hot body to a cold body. The radia- 

 tion of energy of which light is an example is another 

 natural process. 



What is the result of these natural transformations? 

 We notice that they tend toward a dead level of mo- 

 lecular energy. The faster moving molecules lose 

 energy to the slower. The final condition of equilib- 

 rium toward which the universe tends hi these natural 

 processes is then one of uniform temperature. The 



