![]() From 1927 to 1952, several other operators joined Natomas in dredging the district. A pump is fully primed when water is observed flowing out of the discharge end of the pump. This will cause water to become pumped into the foot valve assembly into the pump. In 1916, 11 active dredges yielded more than 2 million worth of gold. Priming the pump on some of the smaller models is accomplished by thrusting the foot valve back and forth under the surface of the water in a reciprocating motion. The company designed and but its own dredges at extensive shops in the town of Natoma. Retorting involves heating the amalgam in a crucible until the mercury vaporizes then the gold can be melted to remove impurities and poured into a mold to create a gold brick. This firm, later known as the Natomas Company, was the principal operator in the district. After removing the riffles and scraping the amalgam out of the box, the process of retorting can begin. ![]() In order to capture as much gold as possible, dredge operators and small-scale placer miners alike added mercury to their sluice boxes because gold and mercury bond chemically to form what is called an amalgam. The orderly piles of waste rock the dredges left behind as they moved across the landscape are called tailings. They did the same work as earlier placer techniques but on an industrial scale, scooping thousands of cubic feet of gravel each day, washing it in revolving tumblers with water from all angles, and running it through multiple sluice boxes. The earliest gold dredges in Alaska arrived in the 1910s, and by the 1930s several dredges were imported to mines along the Yukon River. ![]() Moving gravel by hand is arduous work and often placer gold exists in very small quantities, so it is no surprise that gold miners turned to steam-powered and then diesel-powered machines to make poor ground profitable. ![]()
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