EFFECT OF MOUNTAINS ON HISTORY 543 



ing and smelting works supply the places of the mills and 

 factories of the manufacturing cities. When the ore fails, 

 the army of workers moves on, and the city, once thriving 

 and booming, becomes suddenly simply an aggregation of 

 empty dwellings. 



Modern irrigation has developed many barren uplands 

 into wonderfully successful agricultural districts. 



Effect of Mountains on History. Not only have moun- 

 tains been retreats for the vanquished, but they have been 

 barriers against further conquest by the conquerors. It 

 is very difficult for an army to traverse a mountain range. 

 For a long time the Alps hemmed in the power of Rome. 

 One of the greatest exploits of Hannibal and later of Napo- 

 leon was the passage of these same mountains. 



In our own country the Appalachian Mountains acted 

 for a long time as an impassable barrier to the expansion 

 of the Thirteen Colonies. The trails across them were 

 so long and difficult that it was many years before the fer- 

 tile plains on their western side became populated. The 

 Mohawk valley opened a comparatively easy route at the 

 north, but the Cumberland trail at the south was long, 

 circuitous, and full of places suitable for Indian ambuscade. 



The little mountain country of Switzerland is a buffer 

 state for the rest of Europe. Afghanistan, rough, moun- 

 tainous, and desert, is a buffer state for Asia. It may 

 happen that mountain boundaries are so broad and compli- 

 cated that a little country inserts itself along the boundary 

 of two powerful nations and is able to protect itself from 

 being absorbed by either. The little country of Andorra, 

 containing only 150 square miles, situated in a lofty valley 

 on the southern slope of the Pyrenees, with a population 



