Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 5, Pt. 2

GEOLOGY.
for about twenty miles, without a single hill to break the monotony -of the surface. The wide
plain is dotted with splendid oaks, Quercus Hindsii, which give it a park-like character like the
valley of San Jose.
At the distance of twenty miles from Stockton a gentle undulation of the surface is observable,
and long, gently sloping hills of slight elevation are visible on each side of the road. Horizontal
strata crop out in long lines on their sides, and they appear to be the remains of a former slope
of Tertiary deposits. Hills of this character soon limit the view on each side, and are found as
far as KInight's Ferry, on the Stanislaus. At this point they are no longer low hills, but rise
high above the stream, forming almost precipitous banks, in which the strata are distinctly
exposed. The wide opening made by the river permits the outlines of distant ridges or plateaux
to be seen, and they present a magnificent appearance. The strata lie piled together nearly
2,000 feet thick, and their nearly horizontal edges can be traced for miles. The distant hills are
evidently the margins of a plateau or gentle slope, once the bottom of a Tertiary sea. This
exposure of strata is several miles south of the erry, but similar bluffs, though of less altitude,
face the river a short distance below the crossing. Here the sandstone beds are hard, and the
river flows over them in rapids. The tops of the banks are covered with large, round blocks of
basalt or amygdaloidal volcanic rocks, and they appear to have been derived from the edges of
a horizontal layer in the vicinity. There are indications of a great dyke cutting through the
strata, but it may be older than them, and the beds may have been formed arounltd it. Recent
overflows of basalt are, however, not far distant, and the distant plateau is probably covered-in
part by this roof-like protector from rapid denudation.
Mining operations are conducted all along this part of the Stanislaus, and the tributary
ravines, in the river-drift or gravel and sand of its bed and shores. On crossing the river, and
rising the opposite bank, abundance of round, weather-worn masses of basaltic rock were found
they are probably from a dyke or overflow. The old metamorphic or Azoic slates crop out a
short distance beyond. They are talcose and chloritic, and are nearly vertical; standing out
in high slabs, arranged in lines like grave-stones. They are called grave-stone slatesby the
miners; and, in fact, are the tomb-stones of past ages. The road extends nearly at right
angles to the trend of these slates, and I traversed a vast thickness. The country is open and
undulating, and there are but few trees. The ascent became more and more rapid, and at
Green Spring Cottage the aspect of the landscape had chlanged. Green trees and grass-covered
slopes succeeded to the bare and parched hills. From Green Spring Cottage there is a beautiful
view towards Burns' Ferry, and the edges of distant plateaux are visible, and a gap in them
made by the river. The summit of these plateaux is formed of basalt, and the rock weathers
with bluff margins, precisely as along the San Joaquin at Fort Miller. This plateau at Burns'
Ferry must be miuch more elevated than that seen at the south of Knight's Ferry.
At Montezuma, and in the vicinity, there are extensive alluvial fiats from which much fine
gold is taken. The earth and stones of a great area have been excavated to the bed-rock and
washed.
Jamestown, three miles beyond Montezuma, and four from Sonora, is a thriving mining
village. Wood's Creek, upon which it is situated, was one of the richest for its extent in California, and is celebrated for its abundant yield of gold.
Sonora, though far in the mountains, has its churches, hotels, bath-houses, and other accom
paniments of cities of older and slower growth. It is one of the largest and most thriving
towns in the mining districts south of Mokelumne Hill.
Visited tILe mill of the "Tuolumne Quartz Company." It is provided with an engine of
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