PREFACE 



DURING the collegiate year 1916-1917, the conduct of the 

 Yale Chapter of the honorary scientific society of the Sigma Xi 

 was entrusted to my guidance, and in order to render the meet- 

 ings of the chapter as profitable as possible, a symposium was 

 proposed on the geological and biological evidences for the 

 evolution of our planet and the earth-borne life. I therefore 

 asked such of my colleagues as were authorities on the several 

 subjects 'involved to prepare addresses to be delivered before 

 the chapter and later to be published in the form of the pres- 

 ent book. The course of lectures was as follows : 



THE EVOLUTION OF THE EARTH AND ITS INHABITANTS 



Lecture I. The Origin of the Earth, November 23, 1916, 

 Professor Joseph Barrell. 



Lecture II. The Earth's Changing Surface and Climate, 

 December 13, 1916, Professor Charles Schuchert. 



Lecture III. The Origin of Life, January 24, 1917, Pro- 

 fessor Lorande Loss Woodruf. 



Lecture IV. The Pulse of Life, February 15, 1917, Professor 

 Richard Swann Lull. 



Lecture V. Climate and Civilization, April 20, 1917, Doctor 

 Ellsworth Huntington. 



The scope of the combined essays is of necessity very broad, 

 ranging as it does from a conception of the universe to the 

 trend of modern civilization. Thus the first chapter deals not 

 alone with the genesis of the earth but of the parent solar 

 system, and, the earth having been established, its history is 

 traced until the time of its becoming a fit environment for the 

 abode of life. The second lecture deals with the changing lines 



