232 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 19 3 5 



electricity away from the earth amounting, over the whole surface 

 of the earth, to a current of about 1,000 amperes. Small as this may 

 appear, it is sufficient to bring about a loss of 90 percent of the earth's 

 charge in 10 minutes if there were no means of replenishing the loss. 

 The nature of this replenishment is the mystery referred to. 



So great has been the difficulty of accounting for this replenish- 

 ment that in 1916 G. C. Simpson,^® now director of the British 

 Meteorological Office, raised the question of a possible spontaneous 

 production of a negative charge in the earth's interior, but offered no 

 suggestion as to how this could be brought into line with existing 

 theory. 



In 1926 Swann,^^ who had worked unsuccessfully with the same 

 problem, followed Simpson's lead, but chose the other alternative of 

 a slight annihilation, or as he called it, " death of positive electricty." 

 He was able to bring this into connection with existing electrical 

 theory by generalizing Maxwell's equations. His fundamental idea 

 was that there might be a very slight difference in the properties and 

 behavior of the two electricities. Here again we are reminded of 

 the difference apparently found by Rupp. 



Such a suggestion was not without precedent. Lorentz ^^ in 1900 

 had postulated a difference between the attraction of unlike charges 

 and the repulsion of like charges to account for another mystery — 

 gravitation. It must be admitted that the accepted idea of the 

 absolute equivalence and mirror-image character of the two electric- 

 ities had weakened somewhat when such men as the director of the 

 British Meteorological Office, the director of the Bartol Research 

 Foundation and a Nobel prizeman could join in expressing doubt of 

 its accuracy .^^ 



Swann's theory of the maintenance of the earth's charge is, from 

 the theoretical point of view, the most successful that has yet been 

 advanced. He modifies the equations of Maxwell by introducing 

 two small terms, amounting respectively to one part in 10-^ and five 

 parts in 10^^ of the main term of the classical theory. These addi- 

 tional terms involve the acceleration and time rate of change of 

 positive charge. 



Swann assumed no similar terms for the negative charge, his idea 

 being that there is a slight differential effect in behavior. For sim- 

 plicity, therefore, he introduced a differential term applying only 

 to positive electricty. This assumption enabled him to account for 



=» Simpson, G. C, Monthly Weather Rev., vol. 44, p. 121, 1916. 



^^Swajin, Journ. Franklin Inst, vol. 201, p. 143, 1926. Phil. Mag., vol. 3, p. 1088, 

 1927. 



^ Lorentz, Koninkl. Akad. Wetensch. Amsterdam, Proc. Sec. Sci., vol. 2, p. 559, 1900. 



32 Additional references : More, Phil. Mag., vol. 21, p. 196, 1911. Gleich, Ann. Phys., 

 vol. 83, p. 247, 1927. Anderson, W., Ibid., vol. 85, p. 404, 1928, Press, A., Phil. Mag., 

 vol. 14, p. 758, 1932. 



