260 Bigelow — Magnetic Theory of the Solar Corona. 



towards a solution of the problem. But these same ions are 

 also vibrating and circulating electric charges, and hence they 

 generate a magnetic field about them, so that they may be 

 regarded as constituting minute magnets. Compare papers 

 on the magnetic field caused by moving electric charges, as 

 J. J. Thomson,* O. Heaviside,f H. M. Reese,;); and others. 

 The outcome of this theory is that the air is electrified and 

 also magnetized in situ by the action of radiation on the 

 atomic constituents of it. Thus the two secondary compo- 

 nents of the above curves, namely the magnetic and the elec- 

 tric forces, are intelligible and can be attributed to one 

 fundamental atmospheric process. Furthermore, it will be 

 remembered that I have for several years insisted that sunlight 

 acts upon the earth's magnetic field as if it were itself a mag- 

 netic field, and that to this action the diurnal deflection of the 

 magnetic needle is to be attributed. This was, evidently, an 

 imperfect statement for the theory of ionization recently 

 established, which was not developed at the time of my writ- 

 ing, but it is now perceived that the fundamental basis of the 

 conception is the same in each. This point is further illus- 

 trated in the International Cloud Report, Weather Bureau, 

 1898-99, page 476, where the diurnal wind components and 

 the magnetic deflecting vectors, taken hour by hour, are shown 

 to harmonize and point to one underlying system. The wind 

 vectors are due to the heat contents produced by the radiation, 

 and the magnetic vectors to the ionization of the air induced 

 by the same cause. Thus the entire subject is placed on a 

 working basis, and it can be carried to a definite end by per- 

 fecting our magnetic and electric observations of the atmos- 

 phere. This position is greatly strengthened, also, by what 

 we know of the distribution of the components of the diurnal 

 variations of the barometric pressure§ of the magnetic deflect- 

 ing forces, and of the vapor tension of the atmosphere in lati- 

 tude. Thus, the first component term of the barometric pres- 

 sure is a maximum on the equator and disappears in latitudes 

 65° ; it also vanishes at a moderate altitude above the surface 

 of the ground. The second term in the pressure breaks sharply 

 at the same latitude, and shifts about ninety degrees in the 

 polar regions. Likewise, the diurnal magnetic deflecting 

 forces break abruptly at 65° in latitude,! and reappear in the 

 polar zone at right angles to their place in lower latitudes. 



*Phil. Mag., July, 1889. 

 f 0. Heaviside, Phii. Mag. (5), xxxix, 1889. 

 % H. M. Reese, Astrophysics, Sept., 1900. 



§ International Cloud Report, Chapter 9, Weather Bureau Ann. Rep., 1898-99 

 Forthcoming Report on the Eclipse of Mav 28, 1900. 

 || Bulletin No. 21, Chapter 4, 1898. 



