438 SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 
little drifting done in this mine. I have not the full data for a detailed history of this exploration, 
and in the following description the distances given are only approximate. For the first 500 feet 
the tunnel was in gravel. Then there came 150 feet of clay resting upon gravel, followed by 150 
feet of clay resting upon bed-rock. Beyond the clay the tunnel was in a soft slate for 300 feet, 
and then in pay-gravel, 325 feet farther, to the air-shaft. The shaft is 1,425 feet from the mouth 
of the tunnel. The strata met with in raising the shaft were, — twenty feet of gravel, forty feet of 
pipe-clay, and two hundred feet of volcanic cement. Beyond the air-shaft the tunnel was driven 
for 2,000 feet in bed-rock, with gravel from fifteen to twenty feet over-head. A coarse pay-gravel 
was then followed for 300 feet, to a so-called “lava cement,” containing some coarse and some 
fine boulders, with about two feet of quartz gravel next the bed-rock. At the present face of the 
tunnel there is a thin gravelly cement on the bed-rock, covered with a sandy clay containing good 
impressions of leaves. The gold found is rather fine, and black sand is said to be plentiful. These 
explorations have so far failed to confirm the belief that the main channel lies to the west of that 
in the Bald Mountain mine. At present I am inclined to the behef that the gravel found in the 
North Fork mine, as well as that reported from other places, lying to the west of Alleghany and 
Chips’s Flat, which I was not able to examine in person, does not belong to any continuous and 
independent channel, but was in some way once connected with the more easterly deposits. 
Between Forest City and City of Six the gravel is nowhere exposed to view at the surface of 
the ground. At Rock Creek there used to be a mine worked by means of an incline, which is no 
longer accessible. About a quarter of a mile below the old incline Mr. William Ivelan is driving 
a new tunnel, known as the Ruby Tunnel. The tunnel starts in a soft and clayey slate bed-rock, 
which requires but little blasting, and follows a southeasterly course for about 450 feet, when the 
course is changed to the east, and a branch is started to the northeast. Gravel has been found 
about twenty feet above the main tunnel, and near the roof of the branch. Between these points 
the gravel is continuous, and the bed-rock has a pitch to the east or northeast. My barometric 
measurements cannot, of course, be relied upon to determine with accuracy small differences of 
level, or to settle the question whether or not it is possible for a gravel connection to exist between 
Rock Creek and the Bald Mountain mine. The altitude of the mouth of the Ruby Tunnel I made 
to be 4,800 feet, and Mr. Ivelan’s estimate is, that the gravel in the Ruby Tunnel lies upon a side 
bench from seventy-five to one hundred feet above the deep channel, the level of which is known 
to be below that of the bed of the present Rock Creek. Taking into account the grade of the 
tunnel, and adopting the lower of Mr. Irelan’s estimates, it may be said that the deep channel has 
an altitude of 4,750 feet. The mouth of the Bald Mountain tunnel I made to be 4,489 feet above 
sea-level. If the rise in the tunnel is uniformly four feet to the hundred as far as the shaft, 1,800 
feet from the mouth of the tunnel, the altitude at the bottom of the shaft is 4,561 feet. Between 
this point and the bottom of the Rock Creek incline there is a difference of level of 226 feet, accord- 
ing to the survey made by Mr. I. G. Jones, county surveyor of Sierra County. If these data are 
correct, the altitude of the Rock Creek channel is 4,787 feet, thirty-seven feet higher than I made 
it to be with the barometer. The distance between the shaft and the incline is probably- between 
a mile and a half and two miles, which, supposing the grade of the Bald Mountain channel to con- 
tinue to be as much as four feet to the hundred, would require from one to two hundred feet more 
difference of altitude between the places'than really exists. The grade of the Bald Mountain 
channel, however, grows less as the tunnel increases in length, and I see no reason why there may 
not be an uninterrupted stratum of gravel between the present face of the Bald Mountain tunnel 
and Rock Creek. Against this hypothesis it is urged that the Rock Creek gravel lies in a narrow 
channel, only sixty feet in width, and that the gold of Rock Creek is different in character from 
that of Bald Mountain. I brought with me from Ruby Tunnel a few pieces of gold, given me by 
Mr. Irelan, which have been examined by Mr. Wadsworth, who says of them: ‘“ This gold shows 
the impress of the vein-stone, and while the thinner parts have been bent over and in upon the 
main mass, the grains as a whole seem to have suffered more from wear than from the direct 
pounding of the pebbles upon them. This came from a white clayey or fine sandy bed. The 
