PlunuiUm t<lrcaiii I'irdcj/. 



Fig. 2. View of the flat-bottomed opening tlirough which Upper Cut-olf 

 Creek enters onto the wide flo()d plain of Salt Creek at Phillips School. 

 Salt Creek flood plain is confluent with this flat-bottomed opening, and 

 is beyond the projecting spurs of upland shown at either side of the 

 view. 



valley-flat of Salt Creek. The alignuiont of the valleys of the two streams, 

 the presence of Cut-off Col between the valleys, the ending of the valley 

 of I'piXM- Cut-oft" Creek where the stream turns northward at Phillips 

 School, the more sharply trenched condition of the upper valley, the under- 

 sized stream in the broad gently-sloping lower valley, and the great semi- 

 circular bend of the steep south bluff of the entrenched valley of Salt Creek 

 show clearly that a once continuous stream has been divided and the 

 upper portion caused to empty into Salt Creek valley several miles farther 

 upstream than where the drainage formerly entered. This condition un- 

 doubtedly resulted from the rather extraordinary widening of Salt Creek 

 valley in the Phillips School locality by lateral planation. 



Conditions ^Yhich Favored the Cut-off Piracy.— X number of conditions 

 favored the Cut-off planation piracy. The parent Cut-off Creek flowed 

 almost parallel with Salt Creek in its westward direction near Fairfax. 

 This parallelism was not an extraordinary thing in this small stream, as 

 the southward turn of Salt Creek valley allowed it to come into Salt Creek 

 in a normal manner. (The southward turn of Lower Cut-off Creek is rather 

 exceptional, as it causes the parallelism of the two streams to continue a 

 greater distance than it otherwise would : but a discussion of this condition 

 is not essential to the present problem.) Lateral planation is a normal 

 action taking place in valleys which have reache<l the mature stage. But 

 the conditions in the vicinity of Fairfax are rather favorable for an un- 

 usual amount of lateral planation. The valley here makes an abrupt bend 

 somewhat greater than a right angle. Such a turn should normally cause 

 the waters of the valley to impinge against the outside valley-wall, or in 

 this case on the south bluff. Tt may be noticed that the valley is much 



