CHAPTER II 



THE EARTH'S CHANGING SURFACE AND CLI- 

 MATE DURING GEOLOGIC TIME 



CHARLES SCHUCHERT 



PROFESSOR OF PALEONTOLOGY IN YALE UNIVERSITY 



Uniformity of nature. The previous lecturer in this course 

 had to seek for the probable origin of the earth in far-off space 

 among the stars, examining them through the great telescopes 

 of our time, through the light-sensing chemical plate of the 

 photographic camera, and through the even more wonderful 

 spectroscope. With this knowledge In hand, postulate upon 

 postulate has been tried out through that talismanic study, 

 mathematics, and so through astronomy and the science of 

 numbers there is revealed an earth evolution still hazy, to be 

 further established through geodesy, mechanics, and chemistry 

 before the geologist comes to be its interpreter. Then, hand 

 in hand with the geologist, the paleontologist, or student of 

 ancient life, reveals the organic hordes that have gone on and 

 through whose fossil remains is unraveled the history of the 

 earth. In all of this we see the brotherhood of the sciences 

 and the fundamental postulate of the uniformity of nature. 



The geological time-table. As some geologic terms must 

 be used in this lecture, it is desirable to define them here. The 

 geologic history of the earth Is now divided as follows : 



Present time. 



Psychozoic era. Age of man or Age of reason. 



Includes the present or "Recent time," and the time 

 during which man attained his highest civilization, 

 estimated to be probably less than 30,000 years. 



