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Hydraulic mining techniques, California, 1870s

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Hydraulic mining, California, 1870s

This photo shows hydraulic mining activity at the Malakoff Diggings in the foothills of the Sierra Nevada in the 1870s. Hydraulic mining was a variation on ground sluicing where the water delivered to the site would be shot through a nozzle at high pressure onto the face of the cliff, thereby washing away tons of boulders, gravel, dirt, and, in the hopes of the miners, ounces of gold. These "water cannons" were indeed very powerful—they could throw 185,000 cubic feet of water in an hour with a velocity of 150 feet per second. The environmental destruction they could do was also powerful.