KR. BIRKELAND. M.-N. Kl. 



Moderate terms are used in the cited place p. 609, but my conviction 

 on this principal point of my theories is very strong. And I have got 

 this conviction from eighteen years of general work on the subject, and 

 especially by the comparative analysis of results from the terrella experi- 

 ments (see only »A. P.« p. 580 — 591) on the one hand and observations 

 on positive and negative polar magnetic storms (see »A. P.« p. 536, 540) 

 on the other. 



It must be borne in mind that any one who would uphold the theory 

 that auroral rays and polar magnetic storms are generally produced by 

 positive corpuscle rays of solar origin has to eliminate consciously by 

 some magic a most important fact which by no means can be explained 

 away, viz.: that, in general, positive polar storms occur in the afternoon, 

 Aurora displays in the evening, and negative polar storms in the night 

 with maximum just after midnight. 



If these phenomena were generally produced by positive rays of 

 direct solar origin, they would occur in a manner symmetrical in configu- 

 ration to that described above, but on the morning side instead of the 

 evening side of the earth. 



There is another important fact which ought to be mentioned here. 



By the statistical treatment of all perturbations registered during my 

 Expedition 1902 — 1903 with four stations Mototchkin Schar, Kaafjord, 

 Axeløen, and Dyrafjord, it has been proved that there is an almost abso- 

 lutely calm period in the day when only very small magnetic forces are 

 acting, see »A. P.« Table XCIV and XCVI pp. 537 and 539. For Ma- 

 totchkin Schar and Kaafjord, which lie on or under the lower border of 

 the auroral zone, this calm interval is respectively between 7^ — 14^ and 

 6*1—1411 local time. For the other more elevated stations this interval is 

 considerably shorter and the acting forces are greater. 



Compare how well these results correspond with the precipitation ot 

 cathode rays on the terrella »A. P.« fig. 219 p. 598. Here the magneti- 

 sation of the terrella is so strong that the precipitation zone corresponds 

 exactly to the auroral zone of the earth. It will be observed that there 

 are no rays illuminating the terrella from 6^ or 7^ till about 14*^ for places 

 on the lower border of the precipitation, but places situated on higher 

 latitudes will have a shorter calm period. 



It seems accordingly, that if any positive rays do penetrate into the 

 earth's atmosphere, they can hardly have any perceptible magnetic effect, for 

 their action must be a maximal one just in the period, which is found 

 to be actually quite calm. But in cosmic space positive rays from the sun 

 most probably — even certainly — exist, only they do not seem to arrive 



