458 SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 
lava, 680 feet ; hard rim-rock, 300 feet ; soft rim-rock, 200 feet ; clay, 700 feet For the last 1,700 
feet the tunnel has been entirely in gravel. In the uncompleted air-shaft there were thirty-three 
feet of gravel. Above the gravel the shaft has been in clay for 142 feet. When finished, the shaft 
will be 352 feet deep. The gravel seen in the tunnel was a good clean quartz, carrying some charred 
wood and some poor impressions of leaves. I tried to secure some good specimens to show the 
character of the vegetation, but was not successful. 
I have now traced the old channel from Council Hill to Potosi. In what direction shall I look 
for its higher sources? I am not at all satisfied with the evidence advanced in favor of the theory 
that this channel came from the direction of Pilot Peak and Alturas, — the theory evidently enter- 
tained by Mr. Hendel at the time of the preparation of the report from which an extract is given 
on a previous page.* It is true [ did not examine in detail the whole of the ridge between Potosi 
and Hepsidam ; I only followed the wagon-road between the two places. But I made frequent 
inquiry of such miners as seemed to have the most thorough acquaintance with the whole district, 
and, as a result of these inquiries, combined with my own observations, making proper allowance 
for any warping of the judgment due to considerations of personal interest on the part of those 
from whom I sought information, I am inclined to the opinion that the gravel channel will be 
traced from Potosi through the ridge to its southeastern slope above Poker Flat. The only piece 
of direct evidence that I have, which bears upon this question, is the altitude of the mouth of an 
old tunnel, which is to be seen a little to the south of the Poker Flat road. I made the altitude 
to be only 5,526 feet, or nearly thirty feet below the mouth of Bonanza tunnel and fifty feet below 
the gravel at the present farther end of that tunnel. When making this measurement I had not 
heard of the Cold Caiion mines, and had nothing to guide me to the proper spot at which to take 
the observation. But whether I stumbled by accident upon the old tunnel through which the 
Cold Cafion gravel was worked or not, the parole testimony goes to show that in the Cold Caiion 
mine the bed-rock had a.dip towards Potosi, and that the mine was abandoned only when the 
accumulation of water in the drifts made further work unprofitable. 
But if the channel is traced to Cold Caiion, what then? I cannot answer the question. Stand- 
ing at the mouth of the old tunnel, one has before him the rough, jagged, open amphitheatre of the 
head of Cafion Creek, the opposite side of which he scans in vain for any indication which shall 
guide his future search. As upon the ridge above Hepsidam, so here, I reached a limit beyond 
which I could not go. There is gravel on the opposite side of Cafion Creek, which will be de- 
scribed in the next subsection, but I cannot see any connection between it and the gravel of Cold 
Cation. 
The total fall between Potosi and Council Hill is nearly 1,600 feet ; the distance is not far from 
thirteen miles. The average grade, therefore, is about 122 feet to the mile. This grade is a few 
feet less than the average grade of Slate Creek between the bridge on the road from Potosi to Gib- 
sonville, where the altitude is 5,480 feet, and the Poverty Hill trail at the mouth of Rattlesnake 
Creek, where the altitude is only 4,000 feet. Taking the distance as eleven miles, the grade is 
nearly 135 feet to the mile. The altitude of the bed of Slate Creek at the bridge, on the road from 
La Porte to Portwine, I made to be 4,318 feet. 
The tailings in Slate Creek, which have been accumulating for so many years, must be very rich 
in gold. The appliances for saving gold in this vicinity have been by no means so efficient as 
those in use in the more southern counties, and the average yield of the gravels has been much 
more to the cubic yard washed. At some time in the future a large profit may be expected from 
them. <A specimen taken from the Slate Creek tailings showed partially amalgamated gold. 
Upon the southeastern slope of the ridge, below Poker Flat, there are deposits of gravel, as at 
Wahoo, for instance, which would have been examined had time allowed. ‘Their relations to the 
other gravels upon this and other ridges have not yet been well made out, and I must dismiss them 
with this simple allusion to their existence. 
* See ante, p. 211. 
