Photo: Rischgilz Collection. 



CHARLES DARWIN 



Greatest of naturalists, who made the idea of evolution cur- 

 rent intellectual coin, and in his Origin of Species (1859) made 

 the whole world new. 



Photo: Riichgitz Collection. 



LORD KELVIN 



One of the greatest physicists of the nineteenth century. He 

 estimated the age of the earth at 20,000,000 years. He had not 

 at his disposal, however, the knowledge of recent discoveries, 

 which have resulted in this estimate being very greatly in- 

 creased. 



