404 SUPPLEMENTARY INVESTIGATIONS IN THE GRAVEL REGION. 
much surprised at the discovery and development of a well-defined channel of auriferous gravel 
running at right angles to the present course of the ridge. 
If I had had a few more days to spare I presume that I could have had access to all the ex- 
ploratory works referred to above. There did not seem to be any disposition to exclude me from 
them. Special appointments, however, would have been necessary, for the reason that little or no 
work was then going on. 
Passing from the northern to the southern side of the ridge, we find two principal points to 
attract our attention, the hydraulic banks at Relief Hill, and the drifting at Mount Zion. 
Relief Hill, in a direct line, is only about two miles from North Bloomfield, but in order to 
reach the place I climbed the steep slope of the ridge until I struck the Malakoff ditch, which I 
then followed in all its windings. I chose this route in preference to the wagon-road, because the 
latter, being built at a lower level, would give me no information in regard to the relations of bed- 
rock and lava. The ditch, from the point at which I first struck it, I found to be entirely in slate- 
rock, until I reached a point on one of the spurs above Missouri Caiion, and above the ditch- 
tender’s house. From this point it is entirely in volcanic material as far as Relief Hill, and even 
a little beyond. The first bed-rock that I saw in the ditch after leaving Relief Hill was at a point 
bearing N. 20° E. from the town. The bed-rock was from that time visible in the ditch as far as 
I followed it ; that is, to the beginning of the Washington trail. 
Relief Hill is the highest large body of gravel on the right bank of the South Yuba River. 
Shallow gravel and surface diggings are found occasionally at higher altitudes, as, for instance, at 
Roscoe’s ranch, five miles above Relief Hill, following the line of the ditch, and there may be 
gravel underneath the voleanic flow. Similar small deposits of shallow gravel are said to exist on 
some of the spurs lower down the river, between Relief Hill and Grizzly Hill, but there is no 
reason to suppose that they have any connection with the gravel of the old channel. 
The gravel exposed to view at Relief Hill lies on the high spur which leads down from the 
main ridge between Rocky Ravine on the west and Logan Caiion on the east. The gravel, exclu- 
sive of what is covered by the volcanic tufa, spreads over about two hundred and fifty acres of 
ground, according to my estimates and measurements made on the spot. Considerable work has 
been done at this place from time to time, but hydraulic operations have been suspended since the 
fall of 1875, as I was told by Mr. Penrose. The few houses which make up the town are built 
upon the gravel, and the most of those few were unoccupied at the time I was there. J found Mr. 
Penrose, who acted as my guide for two or three hours, to be apparently well-informed as to what 
had been done in previous years. The three principal claims at Relief Hill are the Union claim, 
comprising about 120 acres of ground on the western and southern sides of the hill, the Eureka 
claim, in the centre of the town, and the Eagle claim, now belonging to the Eureka Lake Com- 
pany, and lying to the east and northeast of the other two. The Eureka ground has been drifted, 
but never worked by the hydraulic process; in the Union claim water has been used to some ex- 
tent, but for the last year or two drifting has been resorted to; the Eagle ground has been worked 
by the hydraulic process exclusively. 
The bed-rock, where exposed to view, is slate. The position of the old channel is unknown, 
but the bed-rock, if the concurrent testimony of the miners is relied upon, “ pitches into the hill,” 
that is, it falls towards the north and west. Further explorations, however, will be needed before 
much that is decisive upon this point can be written. I could not get any special information 
in regard to the Eureka drifts, nor the Union drifts, except that they were driven in an easterly 
direction and had reached a distance of 1,200 feet from the face of the bank. The Great Eastern 
tunnel, which has been begun in Rocky Ravine and driven towards the supposed deep channel, I 
hoped would throw some positive light upon the question of the position of the bed-rock, but my 
hopes have not been realized. I took an observation for altitude at the mouth of the tunnel, which 
I make to be 3,713 feet above sea-level. The following data concerning the tunnel I got from Mr. 
Penrose. Its course for 1,200 feet is N. 27° E. (magnetic), and then for 600 feet farther N. 15° 
W. (magnetic); the grade for 1,000 feet is two inches to twelve feet, and one inch to twelve feet 
