32 [APPENDIX 



Diablo Range for thirty-five miles, where a district of the recent volcanic 

 rocks is again entered, which continue to the head of the Canada San 

 Benito and San Juan, for a distance of about eighty miles. 



Re turning 'on the Grabilan spur of these mountains, and which form 

 the eastern boundary of the Salinas Plains, the primitive rocks are met 

 with for twenty-eight miles, flank^il on the east by the recent igneous 

 rocks of the same age as those appearing at the Santa Anna peaks, 

 twelve miles to the east ; (during one of the convulsions that agitated this 

 part of the country, about four hundred feet of the Galiban Peak, on 

 its northeast side, was fractured and thrown down into a deep ravine 

 at its base,) intrusive dikes have had the effect to change the sedi 

 mentary rocks when found in contact with the same. 



In the Coast Mountains to the west, the granite and serpentine series 

 are. predominant, and on these rest the sedimentary rocks, of early and 

 recent date, unchanged generally, except in local position. 



Crossing the Pajaro Valley and entering the Santa Cruz Mountains, 

 the main ridge is composed of the granite and serpentine rocks on which 

 rest the fossififerous formations as those above mentioned. The primi 

 tive series extend north into the County of San Francisco, but unlike 

 the formations in the County of Santa Cruz ; no tertiaries, containing 

 fossils, are to be found, except in the sandstone forming the point to the 

 west of the North Beach, and here the Pholas and some other shells of 

 present existing species are found. South of the city the trachytes 

 have intruded through the slates, producing considerable disturbance 

 both by uplift and change of structure in the latter ; on the north side 

 of the city, similar features are to be seen, but on a more extensive 

 scale ; among the deep excavations which have been made about Clark's 

 Point, it is found that the stratified rocks have been tilted from the hori 

 zontal position, and in some cases twisted and contorted into every con 

 ceivable position ; at one time presenting a wave-like form, and in the 

 distance of a few yards, passing from this to high angles or vertical ity. 



Northwest of the Telegraph Hill the active causes of this diversity in 

 the appearance of the rocks is seen. Nearly on a line with Dupont 

 street, and fronting the bay, is a dike of the trap rock, passing up 

 through the sedimentary rocks above. A change of structure in the 

 sandstone in contact with the dike is observed. 



This class of rocks (the volcanic) occur at frequent intervals along the 

 bay coast on the west side, and thence into the valley of the Santa Clara. 

 At the distance of four miles south of San Jose they form the low hills 

 that protrude into this valley from the western side, and which are con 

 tinued at intervals to the arroga Llagos, a distance of thirty miles beyond. 



In none of the lower hills on this side of the valley are the volcanic 

 rocks found in contact with the sedimentary formations, until after pas 

 sing the above arroya, and then only after first breaking through fissures 

 in the primitive rocks after reaching the Pescadero. 



The intrusion of these rocks among the primitive series is marked by 

 a discoloration of the rock through which the dike has passed, some 

 times of several inches in breadth on each side of the volcanic vein ; 

 this is more particularly observable where the disturbed rock is of the 

 granite class ; in that case it usually presents a brown, or reddish brown 

 color, and is decidedly more given to decomposition than at a short dis 



