CURRENT BALANCE. The current balance was first de vised by Lord Kelvin in 1883 when he and Joule made the standard current weigher. A highly accurate form of Kelvin cur rent balance is the primary instrument used at standardizing insti tutions to determine the ampere (see INSTRUMENTS: ELECTRICAL, Standard Instruments). The current balance is an electrody namometer type of instrument which is astatic and in which the forces of attraction or repulsion are actually weighed as in an ordinary balance. A dynamometer type instrument depends upon the reaction between fixed and moving coils connected in series. The movement of the movable coil is a measure of the current flowing through the coils and therefore proportional to the E.M.F. impressed at the terminals. The figure on page 88r illustrates the principles on which the current balance operates. (See INSTRU MENTS: ELECTRICAL, Dynamometer Instruments.)