132 Generating Economic Cycles 



One of the very first to take this step was the physi- 

 cist, Kr. Birkeland, of Christiania, whose primary 

 objectives were the cause of magnetic storms and the 

 origin of terrestrial magnetism. Holding as a working 

 hypothesis that magnetic storms are probably traceable 

 to solar bombardment by means of electric corpuscles, 

 he laid the foundation of his work in an elaborate 

 collection of observations relating to the aurora borealis 

 and simultaneous variations in the magnetic needle. 

 By a very rare combination of experimental ingenuity 

 and speculative fertility he extended his electrical 

 theory of cosmical phenomena to the solar corona, the 

 zodiacal light, comets' tails, and Saturn's rings. To 

 throw new light upon his theories he spent a fortune in 

 building observatories in the far north, equipping sail- 

 ing vessels, and organizing scientific expeditions in 

 which he personally suffered the contrasting hardships 

 and dangers of life within the arctic circle and within 

 the tropics, in the Soudan. Whatever may be the even- 

 tual estimate of his theories, his collection of material^ 



electron bombardment extending to greater distances across space, 

 where no residual matter exists; and the fact that the torrent of particles 

 constitutes an electric current of fair strength gives an easy explanation 

 of one class of electric storms; these storms having long been known, by 

 the method of concomitant variations, to be connected with sun- 

 spots and aurorae. The electric nuclei, when they form ions, would 

 also serve as centers of condensation of atmospheric water vapour at 

 high altitudes, and so be liable to affect the rainfall. Moreover, the 

 fact that water vapour condenses more readily on negative than on posi- 

 tive ions, seems to furnish us with one explanation of atmospheric 

 electricity; for a fall of rain would bring down with it a negative charge, 

 and would leave the upper regions positively electrified with respect to 

 the Earth's surface: and this agrees with the known sign of the normal 

 field of electric force in the atmosphere." Lodge, Electrons or the Nature 

 and Properties of Negative Electricity, pp. 168-169. 



1 The Norwegian Aurora Polaris Expedition, 1902-1903. 



