40 STKUCTUKE OF POINT PINOS RANGE, 



of a bluish tint on a fresh fracture, owing to the presence of adularia. This rock, which occu- 

 pies only a few miles of the surface at the shore of the bay, as the mountain rises to a greater 

 elevation further south, also covers a greater width and forms the highest summits of the range, 

 which exceeds 3,500 feet ; as it passes south it becomes more hornblendic and magnesian in its 

 character. East of the granitic axis a mass of slaty, serpentine, and trappean rocks is protruded, 

 forming a second ridge running a parallel course, whose altitude does not reach that of 

 the granitic chain, but which, from its proximity to the plain, hides from the latter the 

 granitic hills, and presents to view its sharp and angular crests. As this igneous rock runs 

 south it sends spurs out into the valley, which, upheaving the later formed strata, narrow the 

 plain so as to reduce it to 2 or 3 miles broad, 10 miles north of Mission San Miguel, and south 

 of that to lessen it merely to the condition of the river bed without a lateral plain. 



The sandstones and overlying beds have been both partially elevated and cut through by 

 these serpentine and trappean rocks ; in places the sandstone is hard, rings to the hammer, 

 and has a slaty appearance. A few miles north of the Mission San Miguel, trappean dykes 

 cross the road, cutting the sandstone at an oblique angle to the line of strike. In the upper 

 beds the calcareous strata are separated by a quartzose bed, 4 to 10 feet thick, which presents 

 the appearance of agate and opalescent quartz veins, 1 to 2 inches thick, and separated a few feet 

 from each other ; three and sometimes four of these veins occur in the sandy bed ; these silicious 

 veins are in places accompanied by serpentine and talcose clays which tinge the edges of the 

 veins green ; when any portion of this vein stone is removed, it is found to be intersected by lines 

 of former fracture cemented anew, giving a pretty agate appearance to the various tints of the 

 quartz lines. These veins mostly correspond to the plane of deposition of the strata in which 

 they are included ; in a few instances they have been seen cutting the strata through at a slight 

 angle. The presence of these veins serve, from their hardness and readiness to recognize them, 

 as a good mark to determine the presence of the upper fossiliferous beds. In themselves they 

 are the evidences of the existence of thermal waters highly charged with soluble silica traversing 

 fissures in the strata and insinuating the fluid between the laminteof deposition. These layers 

 were first observed in leaving the Salinas and ascending the hills in which the San Antonio 

 river heads. Here a better view of the constitution of the Point Pinos chain was had than 

 elsewhere below, when, on account of the width of the plain, the road lay along the river side 

 away from the mountains. 



South of the Mission Solidad, which lies 35 miles up the valley, the mountains converge 

 considerably, and the low foot hills spread into and narrow the plain. The diluvial clays are 

 deep, often more than 40 feet exposed. The yellow sandstones which, from Hill's ranche for 30 

 miles southward, is observed to rise up from the valley with a gentle slope, now disappears, and 

 a whitish argillo-calcareous rock takes its place ; it is probably an upper stratum of the series 

 brought to light by the lesser slope. The paste of the rock is soft, friable, and easily worn down 

 by the elements ; of a slightly green tint, calcareous, and very full of casts of dosinia, venus, 

 natica, &c., (vide Mr. Conrad's report,) many of which were very imperfect; a few pecten 

 impressions were intermingled ; small masses of this rock were scattered over the terrace and the 

 plain beneath. The observed thickness of this bed was about 50 feet, its whole depth not being 

 exposed. On crossing the divort* between the small stream, a tributary of the Salinas, and the 



a " DivoH." — This word expresses fully what no other word at present in use does. The word " divide " is not etymolo- 

 gically applicable, as it does not conveythe idea of altitude as the cause of separation ; while the word divorl implies eleva- 

 tion, the cause of the " divortia aquarum" — whence its derivation also. It is hoped that this expression will meet with 

 favor and application. 



