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Yuba Dredge No. 17

Geology of California's Great Central Valley

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This remarkable floating machine, the last of its kind in California, scoops up ancient Sierran gravel, extracts a minute fraction of fine-grained gold, and discharges the rest behind it. It digs its own pond, slowly migrating over the extensive gravel beds of the Yuba River east of Marysville.
Self-financing self-voyager
Photo (c) 2011 by Andrew Alden, licensed to About.com (fair use policy)
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