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 lie dormant 
till revived by 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 (1797-1875) so successfully rehabilitated the doctrine 
of uniformitarianism 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 
