Gold-Bearing Lodes in Calif or)na. — Hcrshcy. 87 
Trinity river, Swift creek and Stewart's fork, rise on the north- 
western side of the anticUnes and cross those structural 
"ridges." Hence, they cannot be consequent on the structure. 
Now, if we draw a plane through the mountain peaks, we 
reconstruct a supposed ancient plain of denudation of, say, Cre- 
taceous age. This will have an elevation in the country east of 
the main Trinity river of 7,200 to 7,50a feet, sloping gently 
southeastward. Southwestw^ard from that stream, it will rise 
at a low angle, attaining a maximum exceeding 9,000 feet in 
the vicinity of Mt. Thompson of the Cariboo granite range. If 
we compare the present drainage system with the contours of 
the reconstructed plain, we shall find a significant dependence 
of the former on the latter. We shall see that the streams ra- 
diate outward from the highest portion of the supposed pene- 
plain in the Cariboo region, and farther east, flow directly 
down the slope of the ancient plain. Therefore, it seems evi- 
dent that the drainage is consequent upon the deformation of 
an uplifted and practically destroyed peneplain which was 
formed by the denudation to near sea-level of a high mountain 
system due to post-Jurassic folding and faulting. For reasons 
not necessary to detail here, I consider this to have been of 
Cretaceous age, and to have been destroyed by uplift and 
stream dissection at about the opening of the Tertiary era. 
The Miocene base-level (corresponding to the peneplain of 
the Sierra Nevada foot-hills region) occurs 3,500 feet below the 
Cretaceous peneplain level. It is difficult to detect it within 
the limits of the Sierra Costa mountains, but on the southeast, 
an old river deposit or high-level channel of Miocene age oc- 
curs at an altitude of about 3-500 feet A. T. Since its aban- 
donment by the ancient Trinity river, valleys 1,000 feet in depth 
have been eroded beneath its level. In the Sierra Costa region, 
certain "shoulders" on the slopes of the high mountains mav 
represent this old Miocene base-level. 
TJie Mining Districts. 
Three mining districts, situate in the Sierra Costa moun- 
tains, are to be briefly described and discussed in this paper. 
I. The Tamarack district, at the foot of Tamarack peak, 
on the Trinity-Shasta line, about six miles northeast of the vil- 
lage of Cinnabar. The formations here are mainly the so- 
