120 STRUCTURE AND UPHEAVAL OF THE CORDILLERAS. 



brownish granitized rock (protogine?) cuts, running north and south, and dipping 50° east. 

 It is made up of light brown orthose, rhomboidal, and hexahedral mica, with talc ; crystals of 

 schorl intersect the felspar crystals, and traverse them completely. The syenitic rock is very 

 felspathic^ and has two series of divisional planes. 



The coarse salt grass and reeds growing along the river course indicate the character of the 

 water, which is hard, brackish, and curdles soap readily. Behind the new adobe house 

 erected by an American settler, a mile south of camp, (May 31,) there is a fine spring of fresh 

 water, and there is but little doubt that deep wells would supply good water in abundance, but 

 the surface water and the current immediately beneath are saline. 



Between San Felipe and Vallecitas the trail returns somewhat to the west, and traverses the 

 gneissose belt, with porphyry veins, already alluded to, at a point several miles south of where 

 they were noticed, between "Warner's and San Felipe. Indeed, from Warner's rancho to Carrizo 

 is parallel to the trend of the Cordilleras. Six miles below San Felipe the veins of whitish 

 porphyry granite are seen cutting through the igneous rock, (coarse, dark brown, quartzose 

 granite,) dipping 28° west by north. Nine miles below camp, at San Felipe, there is a distinct 

 intrusion of the finer grained granite (protogine) observed through the coarser rock, which has 

 tilted a mass of gneiss rock, one thousand feet in thickness, to an angle of 30°, presenting a large 

 anticlinal axis, the gneiss and mica slate dipping away from it both to the east and west. The 

 hills on the west, at Vallecitas are granitic, while those on the east are gradually, merging into 

 porphyry, or trachyte porphyry, becoming reddish brown and felspathic. These hills are termi- 

 nated by beds of clay and gravel. They have a slight inclination to the southeast, and have a 

 thickness, in some parts of the valley, ranging from 10 to 15 feet. The lower hills of clay are 

 terraced. 



The water at Vallecitas is hard and sulphurous, but not unpleasant to the taste. As many 

 as twenty springs are concentrated near the camping ground ; these ooze out gently, flow 

 down a few yards as a small stream, and then sink into the soil. 



The descent from Vallecitas to Carrizo creek is easy, being down the slope of a valley. Having 

 arrived at Vallecitas, the Sierra may be said to be crossed, and its characters in the mass may be 

 better comprehended. 



The granitic ujAeave which constitutes the great bulk of the chain cannot be less than 40 

 or 45 miles wide from San Pasquale to nine miles east of San Felipe ; many of its summits 

 within these limits reach 7,000 feet, and much of the elevated land has an altitude of 4,000 

 feet. Throughout this great extent it does not appear to have undergone any subsequent 

 alterations by upheaval or intrusion — at least, in its central portions ; but, upon the flanks of 

 the chain, both eastern and western, volcanic rocks of a different date are exposed. 



Between Peiiascitas and San Pasquale are found intrusions of trappean rock of an uncrys- 

 talline augitic character, which occurred posterior to the deposit of the tertiary beds which lie 

 in contact with them. These beds lie in close proximity with the granitic rock, although in no 

 place were they observed in contact ; they dip gently (speaking generally) northeast at a 

 small angle. Although, therefore, the great mass of the sierra has been upraised since the 

 period of their deposition, yet there must have been a granitic chain in existence pi'eviously, 

 upon the slope of which these tertiaries were disposed, and the maximum elevation may have 

 occurred on the eastern or desert border of the sierra. There, as at San Felipe, the granite 

 may be observed upraised, fractured, and injected by a latter granite ; and beds of gneiss and 

 mica slate tilted up, and even separated into small basins. At more elevated portions of the 

 range the gneiss has been observed included in large masses within the granitic rock, as if in 



