28 GEOLOGY. 
inches. In an adjoining mountain this peculiar mineral aggregation of quartz and slates is 
intercalated with great beds of quartz rock ; in one place 100 feet in width. This has a con- 
spicuous cleavage resembling stratification, parallel with the bedding of the slates that adjoin 
it. The quartz rock is granular, of a gray color, and very tough and compact. The outcrops 
of these rocks are considerably obscured by soil, but were sufficient to lead me to conclude that 
there were several parallel beds. They are inclined towards the north, at an angle of 45 
` degrees, and their trend is nearly east and west. They are undoubtedly metamorphic. 
From the summit of this hill there is a magnificent view of the plains of the San Joaquin and 
Tulares, and of the oak groves of the Four Creeks, spreading out into a wide forest, and uniting 
on the verge of the horizon with the dark-green vegetation of the Tulares. On the other side the 
towering summits of the Sierra, white with snow, rise above the purple haze that rests lan- 
guidly on their slopes, and project their bold outlines on the clear depths of the blue air. 
These elevated peaks were estimated to be 9,000 or 10,000 feet in height, and their influence 
upon the climate of the valley is very evident. At night, the cold air from these elevations 
pours down along the ravines and water-courses, seeming to flow in these channels almost 
like the water. It was a general observation in the camp, during our journeying along the 
base of the mountains, that the direction of the wind at night was uniformly down the caiion, 
while during the day it was generally the reverse. 
Four Creeks to Moore's Creek, 26 miles.—On rising from the bottom-land of the Four Creeks, 
on the south side, the surface and soil of the plain is a sandy and gravelly loam, which would 
be exceedingly fertile, if well watered. 
Near Tule river the lower ridges of the mountains on the left are composed of talcose and 
chloritic slates, with masses or beds of magnesian minerals, resembling ordinary serpentine. 
Some of the outcrops have a striking resemblance to trappean rocks. But the series was 
remarkable for the occurrence of some extraordinary beds of perfectly white and amorphous 
carbonate of magnesia, resembling opaque or massive gypsum, or plaster casts, but of finer 
grain and more dense. The outcrops vary from one to six feet in thickness, and stand out 
above the general surface of the ridge. Their snowy-white color and elevated position made 
them conspicuous objects at the distance of several miles. The peculiarly compact and homo- 
geneous character of this mineral, its purity and quantity, and the absence of all traces of 
crystallization or cleavage, and its complete opacity, are worthy of particular notice. It is, in 
all probability, the most remarkable known deposit of the mineral. The action of the weather 
on these masses of rock has produced some singular effects. The surfaces are furrowed and 
grooved in every direction with miniature, crooked channels, that seem to have served to carry 
off the surface water. These chapnels give rise to small ridges, that unite in elevated points, 
and may be imagined to represent, in miniature, the mountains and ravines of the surface of a 
country. These magnesian beds, with the associate serpentine rocks, have the general strike 
or trend of northwest and southeast. 
‘Moore’s Creek to White Creek, 26 miles.—Slates and serpentine, similar to those just described, 
were again seen after crossing Moore’s creek. As these rock formations, and others that were 
observed in the vicinity, had characters indicative of the presence of gold, I prospected the 
surface gravel from the bed of the stream, but without success. I am, however, of the opinion 
that gold exists in that vicinity, and in the foot-hills near the Four Creeks. Cottonwood trees 
* A full description of the mineral will be found in chapter XX. 
