18 [APPENDIX 



changes materially after passing this point, and the magnesian rocks begin 

 to be gradually developed. 



The mountains were again entered fourteen miles above the Canada 

 Solza, and followed for eleven miles, the magnesian rocks were met at 

 short intervals throughout the entire distance. Chlorite and talcose slates 

 with beds of impure serpentine occur, containing actinolite, and in the 

 ravines fragments of chromic iron ; at one locality this mineral was found 

 in considerable quantities. No chromic iron was found in place in any of 

 these rocks, but the detached masses in the ravines indicate deposits to a 

 considerable extent. 



The Panoches were visible from this point and distant about seven miles, 

 bearing per compass south-east by east, and the entire range of hills inter 

 vening leads to the belief that the same class of rocks as those above 

 alluded to, compose the principal rock of this section. This opinion was 

 subsequently corroborated by the results of an exploring party from the 

 Mission San Juan, who were out in search of what had been supposed an 

 argentiferous vein, up the Canada of that San Juan, the ore brought in by 

 this company proved to be an excellent quality of the chromic mineral, 

 containing considerable quantities of the emerald nickel, which is far 

 more valuable than the mineral with which it is associated. 



A line from tie Canada Solza carried east to the Arroya San Juan ter 

 minates at a point four miles north of a sandstone formation lying upon 

 the east declivity of these mountains which contains marine fossils ; those 

 that were sufficiently firm for examination were found to be of present 

 existing species of the Pacific Coast, consisting of Mytilus and Cytherea ; 

 in one part of these tertairy sandstones some fragments of Purpura were 

 found, which are identical with those on the Arroya Pescadero, county of 

 Santa Clara, and the litteral sea beaches on the Straits Carquinez. This 

 was the only deposit of sedimentary rocks found on this spur of the Monte 

 Diablo Eange, and points to a period remote, when the waters of the ocean 

 washed those shores, and furnishes corroborative testimony of the reces 

 sion of the sea from those places by uplift from volcanic agencies below 

 the surface. 



On the west flank of the Gfabilan (which is the most prominent peak on 

 this spur) a bed of primitive limestone occurs, extending from the Canada 

 Yergeles on* the north nearly to the Sierra Chapadero on the south, a dis 

 tance of twelve miles ; it was observed on the lower hills of this part of 

 these mountains only, and at no elevation exceeding five hundred feet 

 above the level of the Salinas Plains. 



At one locality these rocks have been cut through by two dikes of trap, 

 and also a heavy dike of quartz is found on its eastern edge, which runs 

 parallel with the course of the calcareous rocks ; the quartz has cut both 

 the granite and limestone, and thrown both to the west, it is heavily 

 charged with iron, and contains in addition the blue and green carbonate 

 of copper with a little gold. The limestone passes under the Salinas 

 Valley and has a considerable inclination in contact with the intrusive 

 veins above noted ; it contains silver and lead (Argentiferous Galena) in 

 small veins in several places. As the calcareous formation does not show 

 itself on the opposite side of the valley, opposite this locality, the pre 

 sumption is that it underlies the plain at a considerable depth, and should 



