TOPOGRAPHICAL. — TITE SIERRA NEVADA. 



7 



hand the Spanish-Americans have many appellations for the different groups 

 of what we call the " Coast Ranges," but no general one for the whole sys- 

 tem.* It is true that the exact limits of the longitudinal extension of the 

 Sierra have been a subject of much discussion ; but this is a question of 

 theoretical rather than of practical importance. To the ordinary California!!, 

 and for the purposes of the present volume, the Sierra Nevada may unhesi- 

 tatingly be taken as commencing at the lower or southern end of the Great 

 Valley, in the neighborhood of Tejon Pass, and extending to Lassen's Peak, 

 which is very nearly on the same parallel as Redding and Shasta (town) be- 

 fore mentioned as marking the northern limit of the valley. From Lassen's 

 north, the prolongation of the axis of the Sierra is marked by a series of 

 volcanic cones, finally culminating in Mount Shasta itself, which is on almost 

 every side an isolated peak, rising 10,000 feet above its base, and with 

 Lassen's Peak forming the advanced guard of the immense volcanic plateau, 

 which stretches over many thousands of square miles in Northern California, 

 Southern Oregon, and the region lying east and north of this. From Shasta 

 (town) north, the Coast Ranges in Trinity, Klamath, and Del Norte counties 

 assume characters, as to elevation, direction, and geological structure, inter- 

 mediate between those of the Sierra and the Coast Ranges proper. This 

 portion of the State, indeed, lias been less explored by the Geological Survey 

 than any other portion of California, and the relation between the two great 

 ranges are far from being clearly understood.! 



Beginning then at the southern extremity of the Sierra and proceeding 

 north, we find, in general, less elevation of the chain, and at the same time 

 greater complication of structure. But it must be borne in mind that the 

 Sierra Nevada is in reality not only a range of mountains, but a range built 

 tip on the western edge of the great plateau or elevated mass of which the 

 Rocky Mountains form the eastern edge. The Sierra differs from the Pocky 



Mountain ranges, however, in that it marks a descent almost to the sea-level, 

 while the eastern edge of the Cordillera plateau at the east base of the 

 Rocky Mountains is several thousand (five thousand in the latitude of 

 Denver, Colorado) above the sea-level, towards which it is prolonged in a 

 very gently descending incline which has no parallel on the other edge of 



* T 



The higher snow-covered portions of the Rocky Mountains and of the Himalaya are very commonly 

 called by the dwellers at their bases the " Snowy Range"; this is exactly the same name which the 

 Spanish-speaking people gave to the high mountains of California, 



t The eastern slope of the Coast Ranges, north of Clear Lake, has never been explored either geo- 

 graphically or geologically. 



** 



