Report of the committee on magnetic standards, and instruments and methods of aerial magnetic measurements

Abstract

Comparisons of magnetic and electric methods for determining the horizontal intensity of the Earth's magnetic field.—With respect to magnetic standards, the outstanding work during the year was the completion of an indirect comparison between three electro‐magnetic instruments for determining the horizontal intensity of the Earth's magnetic field, viz, the Schuster‐Smith magnetometer of England, the Watanabe electric magnetometer of Japan, and the Carnegie Institution of Washington sine galvanometer designed by Dr. Barnett and constructed by the Department of Terrestrial Magnetism. These comparisons were obtained by Messrs. Parkinson and Brown of the Department of Terrestrial Magnetism of the Carnegie Institution of Washington using standard magnetometers of the Department for the comparisons at the National Physical Laboratory, Teddington, England, and at the magnetic observatory, Kakioka, Japan; the magnetometers were later carefully compared with the sine galvanometer at Washington. The results show that the Schuster‐Smith magnetometer and the sine galvanometer give values differing by less than 1/10,000 part of the value of the horizontal intensity, H, of the Earth's magnetic field, or less. The Watanabe instrument, however, for some reason indicates values greater by 1/3,000 part of H, but field instruments were used for this work and there is somewhat greater uncertainty in the result than for the other comparisons.