3D COMPASS

PROBLEM TO BE SOLVED: To measure declination and inclination of terrestrial magnetism anywhere on the earth, except at places near both the south and north poles since a rod magnet is put in the center of a sphere and, floated on water and indicates the direction of the magnetic lines of the earth's magnetic field as the sphere moves by receiving only the force of the earth's magnetic field. SOLUTION: Parallels of latitude and longitude circles, including magnetic poles as axes, are drawn on the surface of the sphere containing the rod magnet and is put in a transparent sphere, which has a slightly larger inside diameter than that of the sphere. Water is put in both the spheres and then the internal sphere floats. The material of the internal sphere and the amount of the water are adjusted so that the gravity operating on the internal sphere and the buoyance balance with each other and the internal sphere is in the center of the external sphere. When the internal sphere and external sphere comes into contact with each other, the surface tension of the water operates, so that a pointer is stuck inwardly from above and below the external sphere to avoid that. The inclination is read from the tip of the pointer and the parallels of latitude of the internal sphere. The declination, graduated on the azimuth angle ring on the external sphere side, is set in the direction in which the longitudinal circle of the internal sphere indicates and then the true north direction can be found.