257 



the chief problem. Why do not deltas occur on all of the hundreds of 

 streams that score the valley sides? Why did one stream a mile or two 

 long build a delta a few rods in area while a much longer stream near by 



Fig. 2. Brig-gs Delta. 



A. From below. 



B. From above. 



built none? The answer seems to be that such features have no prolonged 

 history, but owe their existence to a single local and brief accident of 

 drainage which did not affect neighboring streams, 

 [17—23003] 



