This method of determining the horizontal intensity of the earth's magnetic field depends on well-known principles, which, however, do not seem to have been applied in exactly this fashion before. A magnet is suspended in a horizontal plane and allowed to vibrate under the joint influence of the earth's field and a known controlling field in the same direction and in either the same or opposite sense. The controlling field is that of two similar circular coils placed a distance apart equal to the radius (arrangement of Gaugain and Helmholtz).
Proceedings of the Iowa Academy of Science
©1924 Iowa Academy of Science, Inc.
Tyndall, E. P. T.
"A Simple Method of Determining Horizontal Intensity of the Earth's Magnetic Field,"
Proceedings of the Iowa Academy of Science, 31(1), 383-384.
Available at: https://scholarworks.uni.edu/pias/vol31/iss1/131