The most precise balance in the world

Lynn Poole distinguishes between weighing and other forms of measurement and comments that the Latin word for balance is "bi-lancis," meaning two dishes, as in the two pan level beam instrument. He shows sketches of other early balances, including the Egyptian first class lever and the Roman steelyard, both still in use today. Other types of scales and the kilogram weight kept by the Bureau of National Standards are shown. Johns Hopkins University chemistry professor Alsoph H. Corwin exhibits the highly precise balance he developed to measure very small samples of rare substances for microchemical manipulations. His assistant, Joseph Walter, demonstrates how magnetism, heat, vibration, and static can interfere with accurate measurements, and Dr. Corwin explains how his balance avoids all of these interferences. Dr. Corwin describes the parts of the balance, including the boron carbide knife edge bearings, and explains its operation. The studio camera also shows what operators of Corwin's balance see to discover the equilibrium point.