22 EVOLUTION 



by Herbert Spencer,* who has perhaps done more than 

 any other to establish and emphasize the general ap- 

 plicability of the evolution idea. For the law of origin 

 by evolution is by no means exclusively confined to 

 the method of coming into existence of the species of 

 animals and plants. On the contrary, it was equally 

 well applied by Spencer himself to describe the manner 

 in which are supposed to have arisen the stars and 

 other heavenly bodies, the geological strata and geo- 

 graphical configuration of the earth, and the various 

 gradations of human society. 



The discovery that certain chemical elements exist 

 which are themselves not immutable has been made 

 since Spencer's time. Quite recently ' the phenomena 

 of radio-activity have forced us to believe that radium 

 is passing continuously into helium,'f and something 

 more than a suspicion has been aroused that radium 

 is itself derived from uranium. Thus the dreams of 

 the alchemists are shown to have been not wholly 

 without foundation, for the probability is strong 



* Spencer gives the following illustration : Regarding the 

 striking together of two bodies as a ' cause,' he points to the 

 following possible ' effects ' : A sound ; other vibrations or 

 movements in the surrounding air ; a disarrangement of the 

 particles of the two bodies in the neighbourhood of the point 

 of collision ; the production of heat, and possibly of a spark 

 i.e., of light. 



Two words in this sentence are placed between inverted 

 commas, to indicate that they are used in a strictly popular 

 sense. The use of the words ' cause ' and ' effect,' though 

 seldom strictly scientific, is often convenient, and if used with 

 caution, there is no reason why they should lead to misunder- 

 standing. See Whetham, ' The Recent Development of 

 Physical Science,' chapter i. 



t Whetham. 



