THE OVERLAND EOUTE — OGDEN TO SAN FRANCISCO. 



221 



to the town of Pinole (pee-no 'lay, a Spanish term used hy the Indians 

 for parched grain or seeds), where the Pinole tuff is in contact ^\^th 



covered by a thick mantle of 



Pinole, 



Population 798. 

 Omaha 1.760 mil- 



Monterey 



the Pleistocene shale. In the cuts southwest of 

 Pinole the rocks exposed are all either steeply in- 

 clined Pliocene tuffs or horizontal Pleistocene beds. 

 At Krieger, where the tracks of the Santa Fe route may be seen 

 approaching the bay front from the south, is a so-called '^ tank farm.'' 

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

 yond the Santa Fe Ime. Beyond Sobrante station is Giant, another 

 powder factory, and beyond that are pottery works which obtain 



one, m the Sierra Nevada. The bay shore near Oakland 

 is largely given over to industrial 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 



from 



Oakland are built. 



vicmi 



San Pablo- 

 Elevation 30 feet. 

 Omaha 1,765 miles. 



Wildcat creeks, there is a gravel 



filled basin. 

 seen near 



gravel 



the 



om 



munic 



We 



water company and both railroads obtain water. 

 west of San Pablo station a line of hills shuts out a view of San 

 Francisco Bay, These hills constitute the Potrero San Pablo,^ so 

 called because, being separated from 



ma 



or 



o 



they were a convenient place in which to pasture horses durin 

 the days of Mexican rule, when fences were practically unknown. 

 The hills arc made up wholly of sandstone belonging to the Fran- 



On the other side of them are wharves, warehouses, 

 and large railway shops belondng: to the Santa Fe system. From 



CISC an group 



!->*"*0 



es 



^ The rocks of the Frauciscaii group 

 comprisesandstoiies, conglomerates, shale, 

 and local masses of varicolored thin- 

 bedded flinty rocks. The flinty rock 



associated 



kno^nl as serpentine, 

 with the serpentine as a rule are masses 

 of cr>'3talline laminated rock that consist 

 largely of the beautiful blue mineral 



consist lai-ely of the siliceous skeletons glancophane and for that reason axe ca led 

 of minute marine animals, low in the scale glaucophane schist. Schist of this char- 



of life, known as Radiolaria, and on this 

 account they are known to geologists a^ 

 radiolarian cherts. All the rocks men- 

 tioned have been intruded here and there 

 by dark igneous rocks (diabase, perido- 

 tite, etc.), wliich generally contain a good 

 deal of magnesia and iron but little silica. 

 The peridotites and related igneous rocks 

 have in large part undergone a chemical 

 and mineralogic change into the rock 



known in comparatively few part 

 of the world, but is ver>' characteristic of 

 the Franciscan group. It has been 

 formed from other rocks through the 

 chemical action knov™ as contact mcta- 

 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 the 

 Coast Ranges. 



/ 



