POCKET MAGNETOMETERS DUAL PURPOSE, TWO COLOR SCALE makes the Model 25 Magnetometer more useful. The upper “Black” scale (the one more usually used) reads directly in gauss of a uniform magnetic field oriented parallel with the centerline of the instrument scale. The lower “Red” scale is used in determining the magnitude and direction of an unknown magnetic field by merely orienting the instrument for maximum reading. When shown in the “Red” scale, at such a maximum reading, direction of the measured field is parallel with the instrument pointer and magnitude in gauss.