CHAPTER VL 



IBE EVOLUTION OP THE EARTH. 



In treating of Evolution in general, it was shown how 

 organic bodies are, by a peculiar concurrence of conditions, 

 enabled to lock up a great deal of motion within a small 

 compass, so that permanent redistributions of structure and 

 function can be effected. From the decisiveness with which 

 this peculiar advantage possessed by organic bodies was 

 indicated, it might have been surmised that in the case of 

 inorganic aggregates an attempt to trace the secondary 

 phenomena of differentiation and integration would prove 

 illusory, owing to the absence of this concurrence of con- 

 ditions. In many inorganic bodies it is true that there does 

 not go on to any notable extent that secondary redistribution 

 which results in increase of heterogeneity. The evolution of 

 a cloud, a rock, or a crystal, is little more than an integration 

 of matter attended by dissipation of motion. In the evolu- 

 tion of the solar system, on the other hand, we have. 

 witnessed an increase in heterogeneity, defmiteness, and 

 coherence that is very marked, though by no means so 

 prominent as in the case of organic evolution. This increase 

 in determinate multiformity, such as it is, is due to the 

 special mechanical principle that in any rotating system of 

 particles, regarded as practically isolated, a steady concentra- 



