PIRATES IN THE MOUNTAINS 57 



river is a liquid saw. The water is toothed 

 with sharp sand and gravel and thus edged will 

 saw its way into hard rock; and saw rapidly if 

 the rock is not hard. If there is an uplift the 

 steepened stream will cut more rapidly; if the 

 land sinks and leaves the river with less grade it 

 will cut less rapidly. The steeper the flow the 

 larger and the more numerous the sharp-edged 

 rocks cutting tools the water carries and thus 

 the more rapidly it cuts. The stream that cap- 

 tures another must dig a deeper, lower channel 

 than the one captured for the latter to pour into. 

 "Many a mountain river is older than the 

 land around it," was one of the most interesting 

 things that the geologist said. " It was there first, 

 was in place when the present mountains began to 

 be uplifted. Rivers have worn down and washed 

 away two or more mountain ranges without 

 losing their place. Every river is likely to have 

 a long life with adventures all the year round. 

 A mountain sometimes rises beneath a river, 

 lifting the river up with it. Mountains have risen 

 right across the channel of a river. The river 

 generally cuts through. A mountain rises slowly, 

 while a river cuts or erodes rapidly. It is an ex- 

 pert in cutting through rock ledges. If the moun- 

 tain rises a thousand feet the river cuts a canon 

 a thousand feet deep. Generally by the time the 

 mountain is uplifted the river has severed it." 



