16 [APPENDIX 



i 



thirteen miles very few sandstones containing fossils were to be seen. In 

 the arroya Caoti the first specimens of scoriaceous lava were met with, 

 this induced a more critical examination of the mountains to the east of 

 the valley than would otherwise have been made. The hills were entered 

 a short distance south of Laguna Seca, and followed thence southerly 

 for eighteen miles. Small patches of fossiliferous rocks are sparingly 

 distributed over the route, the predominating rocks being igneous and 

 composed principally of trachytes and lavas ; from Laguna Seca an 

 almost continuous dike of the latter extends along the western base of 

 the ridge for a distance of near twenty miles. 



As you approach the Eancho Cantine it becomes more cellular than 

 farther north at any point where it was observed. In the vicinity of 

 Grilroy's it has been used for milling purposes, to which it seems admirably 

 adapted, being unequalled in hardness to the best French Buhr. I saw 

 at Gilroy's three sets of these stones which have been in use at that place 

 for several years in flouring wheat. These stones are capable of being 

 split out to the diameter of four feet and the requisite thickness that may 

 be required for the uses of the mill. 



The principal rocks forming the east ridge of the Monte Diablo range, 

 and continuing southeasterly from Gilroy's, are composed of the more 

 recent volcanic series, and are but a part of those above alluded to. At 

 the distance of eight miles from this town, the ridge attains an elevation 

 near three thousand feet, and shoots up into a series of jagged, conical 

 peaks, which maintain this character for sixteen miles south of San 

 Felipe; the pass known as "Pacheco Pass," leading from the Valley 

 Santa Clara to the San Joaquin, is situated among these latter hills and 

 near their northern terminus. 



Nine miles northeast from San Filipe is the well known landmark 

 known as " Pacheco's Peak ;" it is visible for a long distance from the 

 east, west and south, but not from the north owing to the hills between 

 having a considerable altitude and their close proximity on the principle 

 line of travel ; it is formed of trachyte and scoriaceous lavas, and is evi 

 dently the remains of an extinct volcano. 



The Santa Anna mountains stretch in a south-east direction from San 

 Felipe a distance of twelve miles, and from this point sink gradually into 

 an uneven ridge having an altitude varying from one thousand to fifteen 

 hundred feet, but far more rugged than its equivalent north of the 

 Alameda Creek. The section inclusive from the vicinty of Pacheco's to 

 the extreme southeast part of the Santa Anna mountains, has been one 

 of the grand centres of the more recent volcanic disturbances which has 

 imparted to the mountains their present contour ; the greatest amount of 

 local disturbance is confined within a line of distance comprising about 

 eight miles north and south, exerting a considerable elevatory force on 

 the sedimentary rocks of recent date to the west and south-west. 



The disturbance among the latter rocks is manifested in a striking 

 manner on the south-east portion of the "Loma Muertas," (a range, of 

 hills extending from the south-east part of the Santa Clara Yalley across 

 its upper end, dividing this from the Yalley San Juan) which extends 

 also to the fossiliferous rocks near the Mission San Juan, they all 

 have a dip to the west, which is continuous for miles, 



The Eancho Tres Pinos, eight miles south-west of Santa Anna, may 



