Application of vertical variometer‐measurements to the study of secular magnetic variations

Abstract

The advance of terrestrial magnetism as a science has been largely confined to a better understanding of the magnetic fluctuations generated by processes external to the lithosphere. Aside from the obvious fact that the Earth's magnetic field is locally disturbed by magnetic inhomogeneities of the crustal rocks, our knowledge of the Earth's permanent field is purely descriptive. The magnetic charts now available—useful as they are to the navigator and to the surveyor—have not provided magneticians with data adequate for the formulation of even a tentative hypothesis of the origin of the permanent field and of its secular variations. As the matter stands now, it is unlikely that the mere continuation of the present observational activity will yield facts of a new kind within the next 50 years. The study of secular magnetic variations in other ways than by repeating from time to time absolute magnetic measurements at widely scattered stations offers a good chance for achieving further progress.