PHYSIOGRAPHY OF THE BEAVERDELL MAP-AREA. 
49 
a series of terraces upon the valley floors. To-day the cycle of 
erosion is in the stage of youth, its work is represented by the 
deep valleys. Between these valleys lie the remains of a cycle 
in late maturity, the upland, which the young streams will 
presently destroy. The stage to which this youthful cycle has 
progressed may be measured by the fact that the upland remnants 
still cover three times the area occupied by the valleys. 
