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University of California. 



[Vol. i. 



from the Coast Ranges, and emerge through the narrow gorges 

 immediately upon the shore. With the exception of the Russian 

 River, they are comparatively short and unimportant, serving for 

 the drainage of a narrow strip of country along the coast. They 

 are alike, however, without exception, in being practically devoid 

 of either deltas or flood-plains of corrasion. The latter are lacking 

 because the erosive energy of the streams has been chiefly con- 

 cerned with the sinking of their trenches, and little or no lateral 

 corrasion of their canons has yet been effected. Deltas are lacking 

 because the fierce action of an open oceanic shore, with steep off 

 shore profile, permits no embankment to extend beyond the line of 

 the sea-cliffs; and there are no embayments within that line. 

 When, therefore, a little beyond Cape Mendocino the north-bound 

 traveler comes upon the valley of the Eel River, and discovers its 

 beautiful broad flood-plain, he is little prepared for the contrast 

 which its topography presents to that of the streams he has left 

 behind him. When surprise gives way to reflection, a clear and 

 correct perception is obtained of a radical difference in the condi- 

 tions which have controlled the development of the topography in 

 the two cases. 



A cursory inspection of the flood-plain shows that its essential 

 features are due, in all probability, to the lateral corrasion of the 

 stream, and that it is not the surface of an embankment built up in 

 a preexisting valley by delta deposition. This being the case, it is 

 evident that the causes which have differentiated the topography of 

 this stream from that of all the others to the southward must be 

 found in one or more of the following controlling conditions, viz.: 

 (i) The great corrasive energy of the stream, due to its greater 

 volume. (2) The longer local duration of the land at its present 

 altitude relatively to sea level, or (3) the greater susceptibility to 

 stream corrasion of the geological terrane through which it flows. 

 A study of the region leads to the conclusion that the last of these 

 is the effective cause. In its lower stretch the Eel River flows 

 through a terrane which does not occur elsewhere along the portion 

 of the coast now under consideration. The terrane is composed 

 largely of soft, little coherent material, and yields readily to the 

 attack of erosive forces. That the greater volume of the stream 



