22 



miles from Santa Barbara on the road thence to Los Angeles, these mountains 

 have suffered to a small extent comparatively speaking, in those disturbances 

 which have been alluded to as occurring in the coast mountains ; this is manifes 

 ted a few miles east of the rancho Poseto in the county of Los Angeles. At 

 the distance of fifteen miles further in the same direction, and to the northward 

 of the Conejo ranch eight miles, a scoriaceous lava bursts through the base of 

 the mountains, and is tound in the'second range of hills north of the latter lo 

 cality ; this continues at intervals until you enter the locality of the lower moun 

 tains north of the Pesos River, and was found to continue eastwardly as far as 

 the Semma and Papa, beyond which point it was not observable. 



This lava has burst through the primitive rocks and apparently overflowed 

 some few of the sandstones, but the principal effect on the .sedimentary rocks 

 has been that of tilting them from their former position. This volcanic action 

 has continued, apparently almost uninterrupted from the eocene or miocene peri 

 ods down to the present time, though evidently not to so great a degree at pres 

 ent as formerly. This is evidenced by the continued action of a number of small 

 volcanic vents at different distances from the coast, and extending from the 

 county of Luis Obispo to the northern portions of Los Angeles, the most north 

 ern of these vents occurs on the south side of San Simeon Bay at a distance of 

 a little more than three miles from the ocean. As you advance south from -this 

 point the next in importance is found in the hills fronting the coast, on the rancho 

 of Guadalupe in the northern part of the county of Santa Barbara ; another 

 le s active is found on the ranch of Dr. Robbins about five miles from the town 

 of Santa Barbara. Again at the Rincon twelve miles from the town another 

 of these vents is found. These localities emit light, heat and smoke at different 

 intervals during the year, and some of them are dangerous to approach ; they 

 are undoubtedly closely connected with the phenomena of earthquakes that of 

 ten affect this district of country, and which apparently have a tendency to ex 

 pend their principal force in an easterly and southerly dircection. The records 

 of earthquakes that have reached us from this section of country furnish us evi 

 dence in support of this supposition. 



By referring to the number of shocks which have occurred since 26th of No 

 vember, 1851, up to July 14th, 1854, in this part of the State, we shall find that 

 they amounted in the aggregate to 31, and of this number 23 have not been felt 

 north of Luis Obispo, their principal force being exerted south into the ocean 

 for a distance of fifty or sixty miles from the land, (as in the case of the marine 

 volcano 25 miles southeast of the Island of San Clemente, observed by Capt. 

 Cropper and officers of the steamer Cortes on the 1st of March, 1853, arid now 

 known upon American and English charts as " Cortes Hocks,") and east be 

 yond the Colorado River ; (as in the disturbances which occurred on the desert, 

 at Camp Yuma, and south and west of the Colorado River, on the 26th of No 

 vember, 1851, the latter "Mud Geyser" being still active as recent accounts 

 from this section of country declare.) The latter shocks were felt in various 

 portions of Los Angeles county, and were particularly severe at the Mission San 

 Gabriel. 



The effects of these subterranean agents over so large an extent of the south 

 ern part of the State furnish us with the means of judging of what the effect 

 must be. on all the superincumbent strata, over which they exercise an immediate 

 influence. The natural effect must be either to raise or depress the country in 

 rather a uniform manner than otherwise, (as great intensity of action is not man 

 ifest,) and we have no better means of forming an opinion than by an examina 

 tion of the sedimentary groups along the coast-line. A careful examination of 

 these rocks will lead us to conclusions that are not only interesting in a scientific 

 view, but also of a practical and economic character, as their true positions must 



