University of California. 



[Vol. i. 



trunk outlets for systems of far-reaching subsequent drainage. In 

 this way we may account for a portion of the parallel streams which 

 characterize the coast, and of which the Wallala is a notable 

 example. But only a minor portion of these valleys is susceptible 

 of such an explanation. The peneplain which existed prior to the 

 inauguration of the uplift was, at best, only a coastal tract, which 

 graded into a region of stronger relief. In this hilly country the 

 stream courses were still completely under the control of the geolog- 

 ical structure, and flowed in mature subsequent valleys. With the 

 uplift this condition was bequeathed directly to the new cycle, and 

 thus antecedent streams have persisted in their original subse- 

 quent courses, with various adjustments and migrations of divides, 

 throughout the entire uplift. To this class belong the more im- 

 portant streams. The Eel River is a conspicuous example of the 

 class. 



There is also a third class of streams which are consequent upon 

 the later stages of the uplift only. These are usually ifisignificant, 

 but attain some little importance in middle Mendocino County, 

 where, as before stated, the edge of the uplifted plateau has a gentle 

 seaward slope. In these the consequent courses still dominate and 

 the subsequent feeders are feeble. It may be remarked, also, that 

 there is a coastal strip of later Mesozoic (Wallala) and Tertiary 

 rocks whose structural lines do not always conform to those of the 

 older rocks, but exhibit folds whose axes are normal to the coast. 

 Many of the smaller streams which flow normal to the coast are 

 subject to the control of this structure. With the exception of the 

 lower stretch of the Eel River, which is discussed as a special case 

 in the sequel, all of these streams, whatever be their history, flow in 

 valleys or canons which, if regard be paid chiefly to their lower 

 portions, present a degree of advancement in the geomorphic cycle 

 which is practically uniform throughout the region under consider- 

 ation. The influence of the progressive character of the uplift is, 

 however, apparent in the stream topography. The streams present 

 near their mouths a less advanced topography than do their middle 

 stretches. The canons are narrower and more precipitous. The 

 V-shaped profiles are much more acute. The divides are more 

 indefinite, lying on plateaux rather than on ridge crests. This 



