Miscellaneous Publications, 85 



The superstratum of this island is almost entirely composed of the 

 debris of sandstone and jasper rocks, a little slate and bluish earth, 

 and betrays appearances of violence. It is about 900 feet above the 

 level of the sea.— B. 



"The cliffs of the main land, opposite the northwest shore of the 

 Island of Los Angelos afford masses of actynolite and beds of mica 

 slate and talc slate. 



"The Island of Molate, about four miles north of Los Angelos, 

 appears at a distance to be of a red colour, and contains much red 

 jasper, and in a small portion of the cliff black ferruginous slate.— C. 



" In the Island of Yerba Buena, the perpendicular cliffs west of the 

 bay are formed of clay-slate at their base, whilst the superincumbent 

 rock is sandstone, for the' most part in angular masses, and without 

 distinct stratification. The claj^-slate is much contorted, arched, and 

 wavy, assuming an east and west direction, and dipping chiefly to 

 the south at a considerable angle. The sandstone shows itself in the 

 point that forms the eastern part of the bay. 



"The rounded hills of the peninsula on which the Presidio of San 

 Francisco is placed, are variously formed of sandstone, loose sand, 

 serpentine, flinty slate, and jasper. The westernmost hill, which 

 rises from the sea between the fort and the Punta di los Lobos, is 

 serpentine. The north declivity, on which the quadrangle of the 

 Presidio is built, is sandstone. To the eastward of this the serpen- 

 tine again forms a hill of equal if not greater height. The hill to the 

 westward of the jSIission is serpentine. That which rises to the south 

 of it exposes a bare and scarped brow of flinty slate and jasper. 

 Ptocks of a similar nature protrude through the surface of the soil of 

 the hills which separate San Francisco from the extensive valley of 

 Santa Clara (Las Salinas), about six leagues to the southward. These 

 hills are called Sierras di los Samburnos, and terminate on the north 

 in a rocky prominence, in the harbour east of the inlet of the Mission. 



"The range of mountains, Las Sierras del Sur, which bound the 

 above valley to the south, expose flinty slate approaching to jasper, a 

 little northwest of Las Pulgas, and about eighteen miles east-south- 

 east of the Mission of San Francisco. Between the Missions of Santa 

 Clara and Santa Cruz, these mountains form four parallel ranges, the 

 two middle ones highest (about 1,500 feet), with steep declivities ; the 

 first two valleys are narrow ; the third is more extensive, leading to the 

 fourth range, which is considerably lower than the others. The first 

 two ridges are composed of serpentine and a jaspery rock, the third 

 principally of sandstone and occasionally jasper, and the fourth, that 

 nearest Santa Cruz, entirely of sandstone, the upper part being 

 mostly decomposed into loose sand. Petrified bones of a cylindrical 

 form were found in this cliff of sand or loose sandstone in 1827. 



"Where this range approaches the road from Santa Clara to San 

 Juan, nearly half-way, the northern declivity is covered with frag- 

 ments of serpentine, and a little farther on is sandstone and flinty 

 slate. 



"In the neighbourhood of the Mission of San Juan is a sandstone 

 conglomerate, and on the road crossing from San Juan to the plain 

 of Monterey, is sandstone. From the interior of the range between 

 San Juan and Monterey, the inhabitants of Las Animas had brought 

 compact basalt, containing particles of magnetic iron ore, which 



