THE CASCADE KANGE. 207 



a gulf, extending from Tulare Lake to above the town of Red Bluff. Tiiere 

 is, indeed, al)undant reason to suppose the Great Valley did form such a 

 sheet of water witliin the recent period, for the marsh lands bordering- on 

 the lower Sacramento and San Joaquin liivers seem mere continuations of 

 the mud flats of the Bay of San Francisco exposed at low tide, and the 

 relations of the alluvial plains to tlie neighboring hills are indicative of the 

 same conditions, while the character of some of the terraces on the sea- 

 coast demonstrates that the sea-level not long ago was at least over 200 

 feet higher, relatively to the land, than it is now.' 



There would be nothing strange, therefore, in the discovery of brack- 

 ish-water shells or even salt-water remains in the alluvium of the Great 

 Valley, but this would not indicate that the Coast Ranges were non-existent 

 at the time when such mollusks were alive. So, also, the Gulf of California 

 now extends some one hundred and fifty miles to the eastward of the true 

 coast line, or the western limit of Lower California. The fact that Chico 

 fossils are found in central Oregon only proves, therefore, that tlie Cas- 

 cades must have been broken through at one or more points during this 

 period, and not that this range is more recent than the Chico. 



Southern continuation of the Coast Ranges. The Hialn StrUCtUral COUtinUatioU of 



the united Coast Ranges and Sierra Nevada to the southward appears to 

 be the peninsula of Lower California. Mr. Gabb,^ who visited this region, 

 stated that it is possible to trace an uninterrupted granite ridge from the 

 San Gabriel Mountains, north of Los Angeles, through Los Angeles, San 



'Prof. George Davidson has traced from Lower California to Alaska the terraces which line the 

 western coast (Proc. California Acad. Nat. Sci., vol. 5, p. UO). So great is the regularity of the surfaces 

 of some of these terraces that he feels compelled to deny that they have been cut by wave action. Ho 

 considers it probable that ice was the agent. My own opportunities for examining these terraces have 

 been very limited, but in the region between Ft. Ross and Gualala I have studied them with some care. 

 Their topography appeared to me indistinguishable from that of the beaches exposed at low water, and 

 at two points I detected Pholas borings on the terraces at a distance of several miles from one another. 

 One of these points was by estimation 150 feet and the other 250 feet above sea-level. However the 

 terraces of this region were formed, therefore, they have been at sea-level within a period which lias 

 been insuliicient to obliterate extremely superflcial markings in a very soft sandstone. Neither in this 

 region or at Santa Crnz nor on the Faralloue Islands was I able to see the necessity for attributing the 

 excavation of the terraces to any other agency than that of the waves. That there are such terraces 

 for which wave action may seem an inadeqnate explanation I do not of course deny; yet, if the level 

 of the coast were to remain absolutely constant for a very long period, it apnears to me that hard rocks 

 and soft must eventually becnt away to a very nearly uniform depth. Mr. Goodyear (ibid., vol. 4, p. 

 295) has called attention to evidences of oscillation in the level of the eo.ast of Oregon. 



- Geol. Survey California, Geology, vol. 2, appendix, p. 137. 



