254 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 José. l 
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 Knight'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 terry, 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 around 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 outa 
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 slates by 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 changed. 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 much more elevated than that seen at the south of Knight's Ferry. 
At Montezuma, and in the vicinity, there are extensive alluvial flats 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 mi : 
village. Wood’s Creek, upon which it is situated, was one of the richest for its extent in Cali- 
fornia, and is celebrated for its abundant yield of gold. 
Sonora, though far in the mountains, has its churches, hotels, bath-houses, and other — 
paniments of cities of older and slower growth. It is one of the largest and most ۵ 
towns in the mining districts south of Mokelumne Hill. y 
Visited the mill of the “ Tuolumne Quartz Company." It is provided with an engine of 
ning 
