THE GRAVEL: NEAR GRASS VALLEY AND NEVADA CITY. 18] 
top of the Green Mountain shaft, and bearing N. 78° W. (magnetic) from it, is another shaft, in 
which bed-rock rising to the west was found at a depth of only forty feet. This seems almost 
conclusive as to the position of the west rim of the channel at this point. The course of the chan- 
nel being pretty nearly south, it will be seen that it crosses the present Green Mountain Cajion 
at a rather acute angle. From near the mouth of Gas Cafion, which joins Green Mountain 
Caiion a quarter of a mile from Greenhorn, the left bank of Green Mountain Cajion is bed-rock for 
a distance of six or eight hundred feet, while on the right (wes) bank the gravel is seen in or 
near the caiion, and crosses Gas Cafion quite near its mouth. On the right bank of Gas Cajion 
near its junction with Green Mountain Cafion is the Empire Mine and Mill. On the opposite 
side are Fisher’s Diggings. At the Empire Mill there is a tunnel, on a course S. 40° W. (mag- 
netic), which was started in bed-rock, and which, for 400 feet, had bed-rock for its bottom, though 
the top was usually in gravel. The grade of the tunnel was “ water grade,” — say one fourth of an 
inch to twelve feet. At the end of the tunnel the bed-rock was still pitching slightly in a westerly 
direction. Higher up Gas Cajiion, above the boarding-house, there is high bed-rock again, so that 
the eastern and western limits of the channel can be established with a tolerable degree of approxi- 
mation. 
The country between the Empire Mill and Red Dog I did not visit at all. I will only add that, 
taking our altitude determinations as approximately correct, there is a fall of about fifty feet be- 
tween the Empire Mill and Bunker Hill bed-rock ; which gives a very convenient grade, the 
distance being only a little over a mile. At the Gouge-Eye Mine, which lies between these two 
places, we determined an intermediate value for the altitude of the bed-rock. The course of the 
channel, then, may be taken as pretty well established from Quaker Hill southward. 
There was another small extent of country around the heads of Green Mountain Cafion and Gas 
Canon, which I wished to explore for the sake of finding high gravel or overflows, if any existed, 
but was obliged to leave that part of the work unfinished. 
§ 4. Grass Valley and Nevada City. 
The next group of hydraulic mines to be described comprehends those 
situated on both sides of Deer Creek, in the neighborhood of Grass Valley 
and Nevada City. <A reference to the map will show that extensive lava 
flows have made their way from the higher portions of the Sierra far down 
toward the foot-hills on both sides of Deer Creek. The flow which has 
already been described as forming the high and conspicuous ridge known as 
Mount Oro, on the upper waters of the Greenhorn, seems to be connected 
with the gravel deposits at Quaker Hill, being there interrupted for a dis- 
tance of somewhat less than a mile, but again resuming its regular course, 
and continuing, not southwardly parallel with the present Greenhorn, but in 
what may be called the normal southwesterly direction of the Sierra slope. 
This flow forks again just beyond Banner Mountain, one portion continuing 
southwest, and soon terminating at a point three miles east of Grass Valley. 
From this termination a mass of gravel of considerable area extends off to 
the west, nearly reaching the last-mentioned town. On this area are the 
Town Talk mines; and there are also shallow patches of gravel, south of 
these, and between those mines and Osborn Hill. 
