266 EVOLUTION AND THE PRESENT AGE 
of years would much more than suffice for the whole 
process. Now all over the globe the myriad raindrops, 
rushing in rivers to the sea, are with tireless industry 
working to obliterate existing continents, and the 
mean rate at which they are accomplishing this work 
of denudation seems to be about one foot in three 
thousand years. At this rate, and from the action of 
rivers alone, it would take just about two million years 
to wear the whole existing continent of Europe, with 
all its huge mountain masses, down to the sea level. 
It was the application of such considerations by Sir 
Charles Lyell to the great problems of geology, taken 
up one after another, that revolutionized the whole 
study of the earth’s surface. It soon became clear that 
the great catastrophes were entirely unnecessary to 
account for the effects which we see; and for the first 
time in the history of human thought we had brought 
before us, on the most colossal scale, the truth that 
there is nothing in the universe which accomplishes 
so much as the incessant cumulative action of tiny 
causes. This great thought has a significance that is 
manifold and far-reaching; it penetrates the moral 
world as well as the intellectual, and when thoroughly 
grasped, it affects the conduct of our lives as power- 
fully as the direction of our thoughts. It affords a 
suggestive commentary upon that sublime scene in the 
Old Testament which suggested to Mendelssohn the 
greatest of his works, the scene in which Jehovah 
reveals Himself, not in the fire nor the earthquake nor 
the tempest, but in the still, small voice. 
This theory of Lyell’s was at first known as Uni- 
formitarianism as contrasted with Catastrophism. It 
has everywhere won the field, but with sundry qualifi- 
