Tangent-galvanometer combination c. 1910 Hartman & Braun, Frankfurt Germany and George Webber, Zurich Switzerland Wood, copper, brass, bakelite Used to read small currents of electricity 30” high and the copper ring is 20” in diameter This is an instrument that operates as both a galvanometer and a tangent galvanometer. It has a Hartmann & Braun galvanometer sitting within a large George Webber tangent galvanometer. It is a loverly combination of polished wood with lacquered brass fittings, copper ring and dark-tinted cross members. In the tangent mode, the copper ring is placed in the same plane as magnetic north and south. When current is sent through the copper ring, the needle in the galvanometer is deflected to one side or the other. The strength of the current can be calculated as it is proportional to the tangent of the angle of deflection. The instrument is built such that the galvanometer can be lifted off the base and used separately. It is graduated in single degrees with 360 graduations. The galvanometer is 5” in diameter by 6-1/2” high to the top of the glass suspension cover. The delicate needle suspension is intact and it appears fully functional. The tangent galvanometer is 30” high. The three-sided wooden base is 12” per side and 15” high. The copper ring is 20” in diameter. The galvanometer is labeled “Hartman & Braun Frankfurt A/M No. 241 CA3, & OHM. CA. 1000 UMWD”. The base is inscribed “No 684 George Webber Zurich”. This is a nice example of a large tangent/galvanometer. Circa 1910. Antique Scientific Instrument