82 



GUIDEBOOK OF THE WESTEKN UNITED STATES. 



is in broken 



Monter 



smelter 



Beyond Hercules the railroad passes over Monterey sliale to the 



term 



parched gi-ain or seeds), where the Pinole 



Pinole. 



Population 798. 

 Seattle 935 miles. 



Monterey 



a thick mantle of the 



Pleistocene shale. In the cuts southwest of Pinole 

 the rocks exposed are all either steeply inclined 

 Pliocene tuffs or horizontal Pleistocene beds. 



Kriegor^ where the tracks 



ailed 



The oil-storage tanks, which belong to the Standard Oil Co.^ are 

 beyond the Santa Fe line. Beyond Sobrante station is Giant, another 



from 



are pottery works 



The bay shore near Oakland 



largely given over to mdustrial uses, on account of its facilities for 

 rail and water transportation. 



Beyond Giant the foothills retreat from the bay shore and the rail- 

 road enters the broad lowland on which the cities of Berkeley and 



San Pablo. 



>:ievation30fpet. 

 Seattle 940 miles. 



Oakland are built 



m 



Wildcat creeks, there is a ot 



& 



asm. 



Many wells sunk in this gravel may 



seen near the tracks, and from them a municipal 



raUroads obtain 

 1 a line of hdls 



West and south- 



Francisco Bav. 



liills constitute the Potrero San Pablo, so 



mainland 



durin 



Mexican nde, when fences were practically unkno'wn. The hills are 

 made up whoUy of sandstone belonging to the Franciscan group.* 



^ The roclcB of the Franciscan group com- 

 priBO sandstones, congiomerates, ehale, 

 and local masses of varicolored thin- 

 bedded flinty rocks. The flinty rocks 

 consist largely of the siliceouB skeletons of 

 minute marine animals, low in the scale 

 of life, known as Radiolaria, and on this 

 account they are known to geologists as 

 radiolarian cherts. All the rocks men- 

 tioned have been intruded here and there 

 by dark igneous rocks (diabase, perido- 

 tite, etc.), which generally contain a good 

 deal of magnesia and iron but little silica. 

 The peridot ites and related igneous rocks 

 have in large part undergone a chemical 

 and mineralogic change into the rock 



known as serj^entine. Closely associated 

 with the serpentine as a rule are masses 

 of crystalline laminated rock that consist 

 largely of the beautiful blue mineral 

 glaucophane and for that reason are called 

 glaucophane schist. Schist of this char- 

 acter is kno-wTi in comparatively few parts 

 of the world but is very characteristic 

 of the Franciscan group. It has been 

 formed from other rocks through the 

 chemical action known as contact nieta- 

 morphism, set up by adjacent freshly in- 

 truded igneous rocks. The Franciscan 

 group is one of the most widespread and 

 interesting assemblages of rocks in the3 

 Coast ranges* 



