8 B. Silliman on the Deep Placers of 
This general description of the deep-lying placers of the Yuba 
might be greatly extended from my notes, but enough has 
probably been said to convey the impression that the phenom- 
ena here described are on a grand and comprehensive scale, and 
referrable to a general cause long anterior in date to the exist- 
ing river-system; a cause which has been sufficient to break 
down and transport the gold-bearing veins of the Sierras, with 
their associated metamorphic rocks, thus laying up in store for 
human use deposits of the precious metal in amount, on a scale 
far beyond the notions generally prevailing of the nature of 
placer deposits. ; 
Quantity of Gold in the Deep Placers of the Yuba.—The exten- 
sive mining operations which, since 1852, have been carried on 
upon the ridge of land between the South and Middle Yuba riv- 
ers, have supplied the data requisite for a pretty accurate estimate 
of the average value of gold actually saved in mining and wash- 
ing a given quantity of auriferous gravel. Without making an 
exact survey of the ground, it would be impossible to give a 
precise statement of the total quantity of gravel which has been 
washed away, much less of what yet remains to be washed. 
Fortunately, Mr. George Black, a skillful English engineer long 
resident in California, has twice made a reconnoissance of the 
ground now under consideration, and his Report,’ privately 
printed, has been placed at my disposal. I shall use its data 
with freedom so far as they are required to confirm or extend 
my own observations. 
The mining ground in this area stretches along both margins 
of the delta from French Corral, a place near its western ex- 
— in a line pretty closely parallel to the Middle Yuba, 
skirted by the claims known as Birchville, Sweetland’s, Sebas- 
topool, the Kureka claims (at North San Juan), Badger’s Hill, 
through Grizzly Gulch to Woolsey’s Flat, Moore’s Flat, Orleans 
Flat, and Snow Point to Eureka, and thence crossing to the 
South Yuba slopes ; it includes Mt. Zion, Relief Hill, Bloomfield, 
Lake City, Grizzly Hill, Columbia, Pleasant Hill, and Monte- 
zuma, the entire cireuit being over sixty miles. 
But I was fully convinced from my own examinations of this 
ground, in November of last year, that but a very small part of 
the mining ground available for early development and quite 
within easy control of the existing flow of water furnished by 
the Middle Yuba Canal Co. and the Eureka Lake Co. has been 
taken up, much less opened for work. Mr. Black estimates the 
length of the mining claims at present supplied with water by 
the Middle Yuba Canal Co. at five miles, with an average width 
of three hundred and fifty yards, and an average depth of forty 
® Report on the Middle Yuba Canal and Eureka Lake Canal, Nevada Co., Cali- 
fornia. By Gzorex Brack, Civil Engineer. San Francisco, 1864. pp. 32. 
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