FIG. 6. Syncline. 



The Lithosphere 



on one side to slip down below the level of those on 

 the other, and to such a fracture the name of " fault " 

 is given. Faults usually run across country in lines 

 which are approximately straight, and the fractures are 

 generally nearly vertical. The amount of displacement 



caused by a fault is 

 called its " throw," 

 and this may vary 

 from inches in one 

 case to thousands 

 of feet in another. 



It was known to 

 intelligent men as far back as the time of Pythagoras 

 (580 B.C.) that the valleys had been excavated by the 

 rivers that flow in them, and this prepares us for the 

 statement that nearly all the great natural features, 

 mountains, hills and valleys, coast-lines, bays and head- 

 lands, even the great continents themselves, owe their 

 present form to natural agents, such as frost, rain, wind, 

 brooks, rivers, and 

 storm waves 

 known collectively 

 as agents of de- 

 nudation wearing 

 away the surface, 

 and by their action FlG 7-Antidinc. 



upon rocks of diverse resisting power, producing the 

 great variety of physical relief which presents itself to 

 our view. 



We have seen that in early days many were the 

 speculations as to the origin of natural features, and 

 many wild theories were promulgated to account for 

 E 65 



