of 



tURiNG my first boyish exploring trip in the 

 Rocky Mountains I was impressed with 

 the stupendous changes which the upper slope 

 of these mountains had undergone. In places 

 were immense embankments and wild deltas 

 of debris that plainly had come from else- 

 where. In other places the rough edges of the 

 canons and ridges had been trimmed and pol- 

 ished; their cliffs and projections were gone and 

 their surfaces had been swept clean of all loose 

 material. Later, I tried vainly to account for 

 some canon walls being trimmed and polished 

 at the bottom while their upper parts were 

 jagged. In most canons the height of the pol- 

 ishings above the bottom was equal on both 

 walls, with the upper edge of the polish even or 

 level for the entire length of the canon. In one 

 canon, in both floor and walls, were deep lateral 

 scratches in the rocks. 



247 



