HISTORICAL ACCOUNT OF EVOLUTION THEORY 23 



such as volcanic outbursts, earthquakes, and floods, but the main 

 trend of change has been - slow and constant, due largely to erosion 

 and allied phenomena. This view had practically no influence 

 on the ideas of the time and for a long period the idea of catas- 

 trophism triumphed over the more truly evolutionary view of uni- 

 formitarianism ; thus the evolution idea was destined to he dormant 

 till revived bv Charles Darwin. 



THE REAWAKENING OF THE EVOLUTION IDEA 



A number of important influences paved the way for the rehabili- 

 tation of the evolution idea at the hands of the younger Darwin. 

 Which of these was the most important it is difficult to say. Prob- 

 ably Charles Lyell's Principles of Geology and Malthus' On Population 

 were the most suggestive works that Darwin encountered. He was 

 also doubtless influenced by Robert Chambers' Vestiges of Natural 

 History of Creation which appeared in 1844. 



Charles Lyell (1 797-1875) so successfully rehabilitated the doctrine 

 of unif ormitarianism in geology that it became very generally accepted, 

 thus paving the way for a more favorable consideration of the idea of 

 organic evolution. Charles Darwin as a very young man took Lyell's 

 Principles of Geology with him on his voyage on the " Beagle " and read 

 it with the greatest devotion, as is evidenced by his dedication of the 

 journal of his voyage: "To Charles Lyell, Esq., F.R.S., this second 

 edition is dedicated with grateful pleasure, as an acknowledgment 

 that the chief part of whatever scientific merit this Journal and other 

 works of the author may possess, has been derived from studying the 

 well-known, admirable Principles of Geology." 



Malthus' influence on Darwin's ideas is well expressed by Judd 

 as follows: 



"Fifteen months after this 'systematic inquiry' began [referring 

 to Darwin's exhaustive working over of his notes taken during his 

 voyage on the 'Beagle'], Darwin happened to read the celebrated 

 work of Malthus 'On Population' for amusement, and this served as a 

 spark falling on a long prepared train of thought. The idea that as 

 animals and plants multiply in geometrical progression, while the 

 supplies of food and space to be occupied remain nearly constant, 

 and that this must lead to a struggle for existence of the most desperate 

 kind, was by no means new to Darwin, for the elder De Candolle, 

 Lyell, and others had enlarged upon it; yet the facts with regard to 



