Bigelow — Magnetic Theory of the Solar Corona. 259 



south midlatitudes something which reinforces such vectors. 

 If we can give an explanation of these secondary variations, 

 then it follows that the undisturbed primary curve belongs to 

 an external magnetic field, and by inference in this case to the 

 solar field. 



We turn for this purpose to a different research, which is 

 important in this connection. Bauer* has computed the mag- 

 netic line integrals around the several parallels of latitude 

 between 60° north and 60° south, and he found that instead 

 of the summation being zero on each parallel there resulted a 

 well defined variation which is distributed in latitude as shown 

 by the dotted curve of the same diagram. This represents 

 such residuals as would be accounted for by the existence of 

 vertical currents of electricity in the atmosphere, downwards 

 in the tropics and upwards in the higher latitudes as shown by 

 the arrows for positive electrification. Although allowance 

 must be made for the crude materials used in both the above 

 investigations, arising out of the conditions of our scientific 

 observations, which ought to be remedied as soon as prac- 

 ticable, the correlation of these two sets of forces is too strik- 

 ing to be overlooked. The idea is suggested that whatever 

 accounts for one of them carries with it the explanation of the 

 other as well. Meteorologists have already recognized the 

 close connection that the electrical phenomenon has with the 

 conditions known to prevail in the earth's atmosphere. Thus 

 Trabertf refers it to the mechanical transportation of elec- 

 tricity between the upper strata and the surface of the earth 

 through convective currents in connection with precipitation. 

 Elster and Geitel^: refer the phenomenon of atmospheric elec- 

 tricity to the ionization of the atmosphere by solar radiation, 

 and include Bauer's integration in its consequences. This 

 theory may be summarized as follows, but the statement will 

 be carried a step further than the authors referred to above 

 have done. The electromagnetic energy of solar radiation is 

 partly transformed in the atmospheric molecules and atoms, so 

 that positive and negative ions are simultaneously given off; 

 by more rapid diffusion the§ negative ions separate from the 

 positive and produce the electrostatic strain potential observed 

 to exist in the atmosphere. This is confirmed in many ways 

 by Elster and Geitel's analysis. These processes occur chiefly 

 in the latitudes which correspond with the Bauer diagram and 

 are associated with the atmospheric motions of circulation, so 

 that they may be adopted as a step in the right direction 



* Vertical earth-air electric currents, Terrestrial Magnetism, March, 1897. 



f Meteorol. Zeitschrift, November, 1898. 



JTerrestr. Mag.. Dec, 1899; Meteorol. Zeitschr., May, 1900. 



§ John Zeleny, Phil. Mag., July, 1898. 



