19 16. Xo. I. ARE THE SOLAR CORPUSCLE RAYS NKGATIVE OR POSITIVE? 23 



The cosmic rays approach the earth in the same manner as our 

 cathode rays approach the terrella. We must suppose in consequence that 

 the auroral rays in a curtain are formed by just such distinct, propor- 

 tionall}' small groups of cosmic raN's which penetrate deeply into our 

 atmosphere after having successive!}' detached themselves from a larger 

 bundle of rays. The different groups have respectiveh' passed through 

 the magnetic equator ;/, (;/ -f i), (// + 2) etc. times. 



It is relatively easy, from experiments with the terrella, to calculate, 

 within some few per cent, the difference of the times which in this manner 

 should correspond to the entrance into the atmosphere of the ;/ih and the 

 (;/ -\- p)^^ auroral rays at the time when the curtain is formed. 



Such experiments must of course be done with special care for the 

 purpose of securing the great accuracy which is necessary here. 



From earlier experiments which were carried out without special thought 

 of the present determination. I can see that the difference of time in question 

 must be something about one fifth of a second for one ray in the curtain 

 to the next. 



This period, which represents the time the rays take to travel almost 

 from the south auroral zone up to the northern, will also depend on the 

 actual magnetic stiffness of the cosmic rays. 



Out of the mathematical theory alone, considering the earth as an 

 elementar}' magnet, this period of time may also be calculated and perhaps 

 with sufficiently good approximation. 



Now, there are not at present sufficiently exact observations of the 

 periods in question for the auroral rays, but I have just been able in a 

 recent paper to indicate a very exact method of finding this periods ^ 



In the same paper I have predicted, from analogies with my terrella- 

 experiments, that the corpuscular ray precipitations giving rise to polar 

 magnetic storms are also, like the auroral curtains, constituted of coordi- 

 nated distinct proportionally small groups of cosmic rays, which successively 

 detach themselves from a larger bundle of rays. 



At the begiwiijig of a polar storm, such groups of rays are precipi- 

 tated one after another towards the surface of the earth with an interval of 

 time of about one fifth of a second. 



At the beginning of such magnetic storms we have thus to expect 

 strong elementary waves of a period of about ' 5 second. This prediction 

 will be tested within a short time at the Haldde Observatory. 



' On a Possible experimentum cruds for the Theories of Norihlight-cur'ains and Polar 

 Magnetic Storms. Videnskapsselskapets Skrifter. Kristiania 1915. 



