The complex nature of the Earth’s magnetic and electric fields has long puzzled and intrigued investigators. A cursory glance at the subjects of the chapters of this volume will indicate how far-reaching are the problems. Of the geophysical sciences, that dealing with the nature of the Earth’s magnetism and electricity is outstanding in its relations to cosmical phenomena. Unlike some sciences, its lack of ready evidence to any of the human senses makes it a difficult subject to present in even a semi-popular treatment. The attempt has been made to inform the reader of what is known and the ways along which further research is and may be profitably directed. In common with the other volumes in the series “Physics of the Earth,” the aim has been to provide, not a textbook, but a reference book which may stimulate and enlist the interest of a larger group of investigators in terrestrial magnetism and electricity.
The various authors have approached their subjects from many viewpoints. Naturally there will be some overlapping in the treatments and some differences of opinion. Repetition has been eliminated so far as has been possible without interfering with the continuity of thought. Many features in the rapid developments of theory and experiment in the field and in the laboratory of more recent years pave the way for different interpretations by investigators. It is increasingly apparent, however, that, although such differences of interpretation may seem great, they tend toward a harmonious integration in the solution of moot questions. The increasing importance of the application of experimental approach through research outside the Earth’s surface is well evidenced by those chapters dealing with the upper atmosphere.
The chapter on bibliographical notes and selected references includes only the outstanding references in the very large literature of the subject scattered through many scientific reports and magazines in all parts of the world. The first part summarizes—a unique feature in a bibliography — the many sources of publication bearing on, and the many international, national, and private organizations interested in terrestrial magnetism and electricity. These notes and references form a most valuable research tool.
The Subsidiary Committee charged with the preparation of this volume has found the task difficult but lightened by unselfish aid from many sources. In particular, it is indebted to the Carnegie Institution of Washington, which has made freely available the vast store of research, illustration, record, and compilation of its Department of Terrestrial Magnetism during the 35 years of that department’s activities.
Besides the contributors who have so generously given of their time in the preparation of the various chapters, the Committee is indebted to many other investigators and organizations for permission to make free use of their research and data. The members of the staff of the Division of Terrestrial Magnetism and Seismology of the United States Coast and Geodetic Survey must be mentioned; their splendid and long-continued work provides a constantly growing and rich mine of data and demonstrates how necessary is coordinated and planned operation in this field of Earth physics.
The Committee is also indebted to the Division of Physical Sciences for the opportunity to prepare this volume on terrestrial magnetism and electricity and for its patience during the long interval necessary for the assembling of the manuscripts.
For the excellence of the illustrative matter, the authors have to thank W. C. Hendrix for the preparation of the line drawings and maps, and P. G. Ledig and J. W. Green for the photographic work.
Should this volume encourage wider interest in research in geomagnetism and geoelectricity, the Subsidiary Committee and the authors will feel well repaid.