Dredge in Manhattan, Nevada: photographic print

From the Nye County, Nevada Photograph Collection (PH-00221) -- Series VII. Other areas in Nye County -- Subseries VII.I. Wilson Family (Toiyabe Mountains, Nevada). The hopper on the starboard side of the dredge is visible. The dredge processed the gravel through jigs as opposed to sluices. With the volume of material the dredge handled, a sluice would have been impractical. A jig has a diaphragm driven by an electric motor which pulsates. The Yuba jigs were about 42 inches long by 42 inches across. A bed in the jig was filled with steel shot. As the gravel material floated across the steel shot, the jig's pulsating diaphragm raised the steel shot-bed up and gold, being so much heavier than the gravel and the steel shot, would work its way down through the shot-bed. The jig bed usually has a 1/8-inch mesh stainless steel screen so that any gold finer than 1/8 inch will pass through the screen. The jig pulsated between 60 and 100 times a minute, a "steady throb." Gold coarser than 1/8 inch, being very heavy, would be held on top the screen beneath the bed of steel shot.