PART 1 . 



THE SCIENCE OF GEOLOGY AND ITS HISTORY 



Geology includes all knowledge of the origin, history, compo- 

 sition and structure of the earth. 



Before commencing to discuss geology in its present state of 

 progress, it is desirable to consider briefly its history as a science. 



The origin of the world was a matter of interest to the earliest 

 Oriental philosophers no less than to the sages of Greece, and 

 the speculations of these early leaders in thought seem to indi- 

 cate the possession of some accurate knowledge, but we must 

 date the beginning of geologic science from the period when 

 geologic phenomena were first observed and correctly interpreted. 

 For a record of these earliest geologic studies we are mainly 

 indebted to the industry of Sir Charles Lyell.a 



Geology began, about 1000 B. C. with the Egyptian priests 

 who observed that the limestones bordering the valley of the Nile 

 had been cut through by erosion and that marine fossils were 

 exposed. In the sixth century B. C. numerous observations on 

 terrestrial changes are ascribed to Pythagoras, and Xenophanes 

 is said to have observed and mentioned the occurrence of various 

 fossils. Aristotle and others in their writings speak of fossil 

 fishes. Attention was also called by Aristotle to the changing 

 distribution of sea and land in certain localities. From that time 

 to the Christian era, history affords many records of observations 

 on geologic phenomena but no attempt was made to reason from 

 the present to the past or to do more than recognize terrestrial 

 changes contemporaneous with man. 



Some Arabian writers of the 10th century A. D. are credited 

 by Lyell with accurate observations on the origin of mountains 

 and certain changes of sea level, but not till the 16th century 



a Principles of Geology 



