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rsion balance (Physics.), an instrument for estimating very minute forces, as electric or magnetic attractions and repulsions, by the torsion of a very slender wire or fiber having at its lower extremity a horizontal bar or needle, upon which the forces act. -- Torsion scale, a scale for weighing in which the fulcra o…

, unifilar suspension. Unifilar magnetometer (Physics), an instrument which consists of a magnetic bar suspended at its center of gravity by a long thread, constituting a delicate means for accurately measuring magnetic intensities, also for determining declinations of the magnetic needle.

res. -- Variation of the needle (Geog. & Naut.), the angle included between the true and magnetic meridians of a place; the deviation of the direction of a magnetic needle from the true north and south line; -- called also declination of the needle.

An instrument for comparing magnetic forces, esp. in the earth's magnetic field.

s compass with a vernier for the accurate adjustment of the zero point in accordance with magnetic variation. -- Vernier transit, a surveyor's transit instrument with a vernier compass.

uplication, triplication, etc., of spectral lines when the radiations emanate in a strong magnetic field, first observed in 1896 by P. Zeeman, a Dutch physicist, and regarded as an important confirmation of the electromagnetic theory of light.