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BED-ROCK: PLACER COUNTY. 83 
excursion was made into the region at the head of the South Fork of the 
Middle Fork of the American, an important mining district not included 
within the limits of the map. Returning to Georgetown, the explorations 
were continued down the slope of the Sierra to Folsom, and thence upward 
to Placerville, the vicinity of which important and central mining town was 
thoroughly examined, as well as the region at the head of the Cosumnes 
River, between Newtown and Grizzly Flat. The remainder of the season 
was given to the principal mining localities in Amador County, nearly the 
whole of which was gone over. Following the above geographical order, 
pretty nearly, the observations made by Mr. Goodyear will now be given, 
arranged under the various heads previously indicated. 
§ 1. The Lithological Character and Stratigraphical Position of the Bed-Rock. 
Immediately above Newcastle, on the line of the Central Pacific railroad, slates make their 
appearance, and the country between here and Auburn consists partly of slate and partly of granite. 
The slates here, so far as seen, generally strike northwesterly and stand nearly vertical. At Au- 
burn the rocks are hard silicious slates, standing vertically or with a slight inclination to the 
northeast : they strike about N. 20° W. These slates are excessively hard and compact, and can 
with difficulty be broken. Their color varies from light green to almost black. On the stage 
road from Folsom to Auburn, the granite continues until within three miles of the latter place. 
At Iowa Hill, at Wiessler’s Claim, the bed-reck consists entirely of slate, generally very thin- 
bedded, argillaceous, and sometimes apparently more or less talcose. Some of these slates are hard 
and very tough, and are then generally of a dark bluish color ; but other portions are quite soft, and 
then usually white. Their strike varies between N. 15° W. and N. 25° W., and they stand 
nearly vertical. At Wolverine, about two miles northeast of Iowa Hill, the slates strike N. 10°— 
15° W., and have an almost vertical dip. At Metcalf’s Claim, near Roach Hill, the strike of the 
slates is N. 10°—15° W., and their dip 60°— 70° to the southwest. At the Morning Star 
Tunnel, on the southeast side of Indian Caiion, nearly opposite Iowa Hill, the strike of the slates 
is pretty uniformly N. 10° —15° W. At Strawberry Flat, Indian Caiion, a little above Inde- 
pendence Hill, the bed-rock slates have a direction of N. 20° W., and dip at a high angle to the 
southwest. In the southwest pit at Elizabeth Hill, two miles south-southwest of Iowa Hill, the 
slates stand nearly vertical, with the usual predominant strike in this district of N. 15° — 20° W. 
At King’s Hill they strike N. 35° W. and stand vertical. At Refuge Cafion, west of Wisconsin 
Hill, the strike of the slates is N. 50° W.; in the east pit at Elizabeth Hill, a little west of Refuge 
Cajion, it is N. 20° — 25° W, 
At Nahor’s Claim, in Green Valley Gorge, about five miles northeast of Iowa Hill, the bed-rock 
is entirely serpentine, and it is said that this rock can be traced for many miles north and south of 
this point ; Brimstone Plains, about four miles south-southeast of the Green Valley Gorge, is said 
to be on this belt of serpentine. At the Mountain Gate Tunnel, near Damascus, four miles east 
of Green Valley Gorge, the bed-rock is a very fine-grained, thin-bedded clay-slate, which, if a little 
harder, might make good roofing-slate ; its dip is nearly vertical, with a slight inclination some- 
times to one side and sometimes to the other; strike N. 10°—15° W. The color of these slates 
is variable, the lighter colored being the softest ; the dark bluish-black varieties are often filled with 
small cubical crystals of pyrites. In the Lower Tunnel the slate is everywhere dark in color. At the 
Cement Mill Claim, near Damascus, the slate is more or less talcose, and some of it very much so. 
The summit of Secret Mountain, on the road from Damascus to Canada Hill, near the head of 
