GEOLOGY WESTERN RANGE OF SIERRA NEVADA. 29 



limit, and that anterior to the emergence of the Californian valley or the coast mountains, the 

 ocean dashed its waves against a continuous iron-bound coast, formed by the great Californian 

 range. Of this coast Mount Shasta was a high and prominent headland. 



With the subsequent elevation of the coast mountains, the entire western portion of the con 

 tinent was doubtless considerably raised, and, like the higher, the lower terrace was bordered 

 by mountain ranges, which presented to the Pacific a second continuous wall, on which its 

 waves, though borne on by all the accumulated momentum of their long and unobstructed 

 course, are still impotently beating. 



I think we have evidence, derived from various sources, that trie elevation of the western 

 coast continued long after it reached the present level, and that since its maximum height 

 was attained it has suffered a depression of many hundred feet. I shall, however, have occasion 

 to return to this subject when speaking of the Cascade mountains, and will, therefore, leave it 

 till the facts there to be gained can be brought to bear upon it. 



The continuity of the present coast mountains of California and Oregon can scarcely be 

 doubted. The fossiliferous sandstones of Monterey, Santa Clara, San Francisco, Port Orford, 

 Coose bay, Astoria, and the Cowlitz, are all apparently of the same age. Though presenting 

 marked local peculiarities, they have a common character both in their lithological features and 

 in their fossils, and are to be referred to a common period certainly not older than the 

 Miocene. 



In going from the mouth of the Columbia to San Francisco by sea, the coast seems formed of 

 a continuous mountain chain, which is constantly in sight, and which produces, throughout 

 nearly the entire distance, a bold, rocky, &quot; iron-bound&quot; shore. To this general rule the limited 

 areas of level land in the valleys of the Umpqua, Coquille, Kogue, and Klamath rivers, form 

 scarcely an exception. 



As far north of San Francisco as Cape Mendocino the coast mountains have the same general 

 northwest trend ; and a more plausible supposition than that the Cascades form the continuation 

 of the coast mountains would be, that the latter ranges terminate at Cape Mendocino, and that 

 the coast mountains of Oregon were a continuation of the Sierra Nevada. It is not necessary 

 to suppose this, however, but it is sufficient to consider the coast mountains of Oregon as the 

 coast mountains of California deflected from the trend which they preserve below Cape Mendo 

 cino, and that the ranges of the coast and of the interior inosculate on either side of the parallel 

 of 42 in the Calapooya, Umpqua, and Siskiyou mountains. 



The structure of these subordinate ranges has as yet received but little attention from geolo 

 gists, though it presents some very interesting problems, which, aside from their bearing on 

 the local geology of the far west, will perhaps throw some light on the question of the synchon- 

 isrn of parallel axes of elevation, and the constancy of trend in the same line of upheaval. 



Nor is the question of the relations of Mount Shasta to the coast mountains or Sierra Nevada 

 one of merely abstract interest, but of the highest practical value in determining the relative age 

 of these two mountain systems, and especially in fixing the age of the metamorphic limestones 

 and slates of the Sierra Nevada, which as yet have yielded no fossils. If, as seems probable, 

 the fossiliferous limestones of the mountains connected with Mount Shasta shall prove to be 

 continuous with the limestones of the Sierra Nevada, referred to above, they will, perhaps, serve 

 as a key by which to unlock the whole structure and age of the great &quot; Californian range.&quot; 



