PART I. ON MAGNETIC STORMS. CHAP. IV. 315 



developed by J. J. Thomson ( 1 ), Larmor and Lorentz, of regarding the atom as a complicated structure 

 consisting of charged parts in rapid oscillatory or orbital motion in regard to one another". 



Under the temperature-conditions prevailing in the sun, it is possible that ordinary matter may be 

 so radio-active, that it is not necessary to assume the presence in great quantities of the radio-elements 

 known in ordinary temperatures. 



It was pointed out by Rutherford and Soddy (-), that the maintenance of the sun's heat for long 

 intervals of time did not present any fundamental difficulty, if a process of disintegration such as occurs 

 in the radio-elements were supposed to be taking place in the sun. 



We may perhaps succeed, in the way here indicated, in obtaining a distinct idea of the amount of 

 heat that can be developed in the sun by disintegration ; and thus an important contribution will be made 

 to the solution of the old, and to natural philosophy so important, question of the origin of the sun's heat. 



(') I see with great satisfaction that Sir J. J. Thomson, in his classic research on the nature of the cathode rays (Phil. Mag. 

 Number CCLXIX, October 1897), in which we find the first definite experimental evidence towards proving that the chemical 

 atom is not the smallest unit of matter, has taken as his starting-point my discovery that the magnetic deviation of cathode rays 

 depends only upon the tension between cathode and anode, if the magnetic force is constant. (See Birkeland, Compt. Rend., 

 Sept. 28, 1896.) This theorem has been verified by Sir J. J. Thomson, 1. c., and W. Kaufmann, Wied. Ann. Vol. LXI. 

 No. 7, 1897. 



( a ) Phil. Mag., May, 1903. 



