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 upheave 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 Penascitas 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 previously, 
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 
