JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. III. JANUARY 4, 1913 No. 1 



TERRESTRIAL MAGNETISM.— A consistent theory of the 

 origin of the Earth's magnetic field. '^ L. A. Bauer, Department 

 of Terrestrial Magnetism, Carnegie Institution of Washington. 



Various investigations by well-known physicists have estab- 

 lished the fact that electricity is an essential and possibly the only 

 constituent of matter. Negative electrons can be obtained from 

 practically any form of matter, by heating, by the action of ultra- 

 violet light, by chemical means, and perhaps also by the apphca- 

 tion of suitable mechanical forces; they are thus proved to be a 

 universal constituent of matter. Matter electrically neutral is 

 supposed to contain equal amounts of positive and negative elec- 

 tricity. We may regard the Earth as a great reservoir of elec- 

 tricity, the two opposite total charges being apparently very nearly 

 balanced. If it turns out that owing to some cause the one kind 

 of elemental charge is, on the average, farther from the center of 

 the Earth than the opposite kind, then because of this difference 

 in distance and of the rotation of the charges with the Earth 

 there will result a magnetic field perhaps of sufficient strength, to 

 be detected by magnetic observations on the surface of the Earth. 



Sutherland (1900-'03)2 probably first advanced the idea that 

 the Earth's magnetic field may be caused by the rotation with the 

 Earth of two opposite and equal electric charges distributed thru 

 the Earth and supposed to be contained within two concentric 

 spheres whose radii differ by an amount which he found to be of 

 the order of the radius of an ordinary molecule. Previously, 

 however, Schuster (1891 and 1892) and Lord Kelvin (1892) had 



1 Presented before the Philosophical Society of Washington, December 7, 1912; 

 for fuller publication see Terrestrial Magnetism, Vol. 18, 1913. 



2 Sutherland, William, Terrestrial Magnetism, first in vol. 5, 1900, p. 73, and 

 later, in improved form, in vol. 8, 1903, p. 49; see also same journal, vol. 9, p. 

 167, and 13, p 155. 



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