264 THE EARTH'S CRUST 



Atlantic, was terrorless. While less favored and hardy 

 sailors were dodging from bay to bay along the shore always 

 in sight of land, they were pushing boldly west, guided 



A NORWAY VILLAGE AT THE HEAD OF A FIORD 



only by the beacons of the sky, and discovering Iceland, 

 Greenland, and the American continent. 



Hills and Mountains. Irregular elevations of the 

 earth's surface are called hills, or mountains when they are 

 of considerable height. In the general use of these terms 

 there is no exact line of separation. Elevations which in 

 mountain regions would be called hills would in a flat region 

 be called mountains. As a rule, elevations are not termed 

 mountains unless they are at least 2000 feet high. But if 

 the general elevation of the country is great, as in the lofty 



