180 AKTSITJAL REPORT SMITHSONIAN INSTITUTION, 1942 



The picture of magnetic phenomena is incomplete if viewed only 

 in a man-made laboratory, even though we can now produce 

 there an artificial magnetic field within a space of a cubic inch which 

 is 100,000 and more times as intense as that of the earth. For- 

 tunately, Nature provides not only the earth and its atmosphere as a 

 great magnetic laboratory but also continuously performs experi- 

 ments, utilizing as apparatus the sun, the moon, and the radiations 

 from space. The interpretation of observable data in so vast a 

 laboratoiy requires special types of research and, in unique degree, 

 world-wide coordination of data and experiment. No single well- 

 planned experiment or observation can solve the problems presented. 

 Observations must be made in all x^arts of the world and must be 

 continued over a long period. Techniques for the organization and 

 interpretation of these data must be developed and experimental 

 researches must be conducted along lines which will supply informa- 

 tion on basic properties related to the subject. Thus it is only 

 through mutual assistance and cooperation of investigators in 

 geo]3hysics, in geology, in astronomy, in physics, and in mathema- 

 tics that we may hope to forward interpretation of natural phenom- 

 ena. Progress in the earth sciences is not the result of individual 

 research; it proceeds not from the isolated work of the few, but 

 from the coordinated efforts of the many. Truly, some individuals 

 may contribute more than others to this evolution of understanding, 

 but their power to contribute is to a large extent determined by the 

 works of their predecessors and of their colleagues. 



The geomagnetic field extends far out into the atmosphere and be- 

 yond it. Even 4,000 miles above us it is still one-eighth as great as 

 at the earth's surface. Our globe may be regarded as approximately 

 a uniformly magnetized sphere with its axis making an angle of 

 ll.°5 with the axis of rotation. Although but feebly magnetized as 

 compared with the magnetization attainable in high-grade magnet 

 steels, the average intensity of magnetization is many orders of 

 magnitude greater than that observed in ordinary crustal rocks. Ap- 

 preciable irregularities in the field exist, but they do not cause 

 great departures from the field which would be produced by the 

 hypothetical uniform magnetization. The moments of the uniform 

 portion of the earth's magnetism, the axial, and the equatorial com- 

 ponents in centimeter-gram-second units, as determined by Bauer's 

 analysis of available data in 1923, are il/=8.04XlO-^ ^^^=7.88X10", 

 and il/e = 1.60X10-% respectively. If the magnetism were distributed 

 uniformly throughout the earth's volume, the average intensity of 

 magnetization would be 0.074 centimeter-gram-second unit. A 

 general idea of the field may be obtained by the distribution of iron 

 filings over a disk magnet, but in reality the earth's field is much more 

 complicated. 



