In 1903, a water engineer named Allen Hazen described a stick for measuring turbidity that he had designed for the U.S. Geological Survey. In principle, wrote Hazen, “it depends upon the distance beneath the surface of the water at which a platinum wire one millimeter in diameter can just be seen, the light being full and strong, but not direct sunlight.” The Water Resources Branch of the U.S.G.S. transferred this example of that instrument to the Smithsonian in 1908.
Ref: Allen Hazen, “The Physical Properties of Water,” Journal of the New England Water Works Association 17 (1903): 21-27.
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