xxviii INTEODUCTION. 



f^ 



ranges, whicli forms tlie '' Golden Gate " of San Prancisco 

 The sea enters throngli the narrow channel, and spreads on^ '.'. 

 into three large basins, protected on all sides by mountain: 

 belonging to the coast ranges, thus forming the best an^^ 

 largest harbour in the world. 



Between the coast ranges and the lofty Sierra Nevada lies * 

 a wide plain or valley, averaging some sixty miles across, mid.j 

 extending north and south for nearly the entire length of the 

 State. The waters which flow from the western slope of the 

 Sierras and collect in this inland valley cannot penetrate thefc 

 coast ranges, and go direct to the sea. So those of Souther 

 California form the San Joaquin Eiver, ai\d those of IS'orthcr 

 California, the Sacramento ; tlie former runs to the northward 

 and the latter to the southward, in the trough between th 

 outer and inner mountain chains^ and both empty themselyvj 

 into the Eay of San Francisco. This is the drainage syste 

 of California. 



I have briefly indicated the com^se which the general ri 

 or upheaval of the continent has taken. "We will now considi 

 the excrescences and iiTcgularities on its suiface. 



The entire country between the Alleghanies (Appalachian f| 

 range) and the " Summit Plateau," which extends from th ^i 

 Gulf of Mexico in the South to the watershed of Hudson 

 Eaj in the J^orth, is mainly one vast flat for thousands < 



k 



square miles in the praii-ie States east of the Mississippi ; ] 

 or less undulating on the western plains, most depressed n 

 the valleys of the Mississippi, Ohio, and Missouri, and onl/ 

 sufficientlv elevated at its northern limit to determine the 



I 



4 



of the waters in the two opposite directions, north and soi 

 Scarcely a trace of volcanic disturbance is to be seen in 

 this vast region. On the " Summit Plateau," however, moun; 

 tains for the first time rise from the plains. All along t^i 



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