vi PREFACE 



of demarcation between land and sea, the rise and growth of 

 continents, the formation and severance of land-bridges, and 

 the climatic changes which are recorded for geologic time. 

 The physical environment once established, Professor Wood- 

 ruff tells what we know and do not know of the origin of life. 

 This is largely an academic discussion of the several theories 

 which have been advanced to account for the evolution of life- 

 less into living matter, for from the nature of the problem 

 evidences of direct observation are not available. The lecture 

 on the pulse of life attempts to link up cause and effect; to find 

 those forces which are responsible for the more or less 

 rhythmic accelerations of evolution shown by the fossil record. 

 The main cause is found to be climatic change, which in turn 

 has as a chief controlling factor earth shrinkage and the con- 

 sequent warping of the crust discussed in the second lecture. 

 The pulse of life applies not alone to the evolution of animals 

 and plants, but also to mankind. How climatic changes have 

 influenced the growth of civilization and the formation of 

 racial characteristics of mentality is set forth in the last lecture, 

 that by Doctor Huntington. In so far as possible, these essays 

 are the fruits of the original research of their several authors, 

 which in certain instances are set forth here for the first time. 

 The treatment of the entire subject and the marshaling of the 

 facts thus assembled are entirely new. 



I am deeply grateful to my colleagues, not only for their 

 having accepted the tasks thus laid upon them, which in several 

 instances implied new and extensive research, but also for the 

 success with which the lectures were presented, as attested by 

 the society. 



RICHARD SWANN LULL, 

 President, Yale Chapter, Sigma XI. 



1916-1917. 

 Yale University, 



December I, /<?//. 



