14 



west by the trap rocks, and on the northeast, by coarse granites and sienites, at 

 times composed almost exclusively of massive hornblende, and at others consid 

 erable quantities of the latter is found imbedded among the other primitive rocks. 

 The primitive group of this section of the country, exhibits itself in a belt of 

 about one and a half miles in breadth, and is most evidently contemporaneous 

 with the rocks forming the Santa Cruz mountains, and that part of the coast 

 line, extending from Point Pinos south to the northern line of the county of 

 San Luis Obispo. 



Among the magnesian rocks of this district there were seen many small spec 

 imens of the chromic iron, but none in such massive quantities as that 'noticed 

 in the Gabilan Spur, in the vicinity of the Sierra Panoches, near the southern 

 junction of this spur, with the Monte Diablo range. The talcose varieties of 

 the rocks of these mountains, as well also as the sienites, and granites, have been 

 intruded and dislocated by the quartz, but no veins of any considerable magni 

 tude were met with, and there was but little indication of any auriferous de 

 posits within them. 



On the head of a small creek which is probably a tributary of one of the 

 southern branches of the Nacismiento, a heavy bed of chlorite slate makes its 

 appearance, having a strike east and west and dipping to the south with a high 

 angle. This bed is cut through by a dike of trap rock having a dark grey col 

 or, and immediately adjoining the latter is a small vein of quartz some nine in 

 ches diameter, holding the same course and having a westerly dip. This vein 

 contains galena, arifcl sulphuret of molybdenum, holding the same relations of 

 mineral disposition, that are found to exist in the vicinity of the Pittsburg Mine 

 in the county of Nevada. 



I was unable to discover any valuable metallic associations in any of the rocks 

 belonging to this group, and am forced as a consequence to say, that in this in 

 stance, the metallic associations hitherto found to be unexceptionable in all other 

 parts of the State, viz : of gold in quartzose and talcose rocks, when found ad 

 joining each other, does not hold good in this instance, it is one of the very few 

 exceptions apparently to that general rule. 



On the west flank of the eastern ridges, and at the distance of about twenty- 

 five miles from the rancho Santa Maria, there are beds of a crystalline or pri 

 mary limestone, similar in all its general characteristics with that found in the 

 vicinity of Santa Cruz ; a large proportion of this calcareous rock, possesses a 

 high crystalline character, and is unsuited for other purposes than the manufac 

 ture of lime. On a small valley to the west of this bed and at the distance of 

 about half a mile west, a heavy deposit of calcareous travertin is found, but like 

 the toro beds in the county of Monterey, the springs that rise to the deposit, 

 seem no longer to exist ; this bed covered an area of nearly one-fourth of a 

 mile, and having a depth of nearly seven feet. 



The geological position of these limestones is among the primitive rocks like 

 its equivalents among the more northern parts of the same mountain chain, and 

 is the same in age as that group extending through three hundred miles of the 

 Sierra Nevada. 



From the valley above alluded to, this rock extends south in detached groups 

 or beds for a distance of about thirty miles, and will be iouud on the west flank 

 of this line of ridges to a point nearly due east of the head waters of the Rio 

 Santa Clara in the county of Santa Barbara. A similar group of these rocks 

 is also met with near Lake Elizabeth, near the main waggon road from Santa 

 Barbara to the Canada de los Ubas and the Tejon Reserve. 



In the canon of the rancho San Francisco the limestone is frequently met 

 with on the sides of the hills to the left of the road, but at this locality it can 

 not be considered in situ. 



The rocks have been carefully examined for organic remains, but in no instance 



