MOUNTAINS; MINING; FORESTRY 207 



The material removed in tunneling is usually taken to the 

 mouth of the tunnel, and there dumped on- the mountain 

 side. For one mine in operation, there are many heaps of 

 "dump" which show where unsuccessful openings have 

 been made. 



FIG. 107. MARSHALL PASS ON THE DENVER AND Rio GRANDE 

 RAILROAD, COLORADO 



This is one of the highest mountain passes (nearly 11,000 ft.) in the 

 Rocky Mountains. 1. How many distinct levels of track are seen on 

 this side of the pass? 2. The road rises about 3,000 ft. in 25 miles. What 

 is the average rise per mile? 



231. The Influence of Mountains. The location of 

 mountain ranges has had a great influence upon human his- 

 tory. In olden times mountain chains were such obstructions 

 to travel that people living on one side knew nothing of those 

 on the other. The Pyrenees, the Caucasus Mountains, the 

 Andes, and the Himalayas are examples of barriers between 



