TUKE SKY PHENOMENA 15 



Pole or, at any rate, about the magnetic pole. As a matter of 

 fact, the zone of greatest frequency is far south of the pole, and 

 north of this zone the displays are seen most often in the southern 

 sky. Another belief, sometimes pictured in artists' sketches, is 

 that the rays proceed from a point in the northern horizon, 

 spreading out fanwise. As stated before, they are really almost 

 vertical, following approximately the lines of magnetic inclination 

 or dip. The aurora itself, of course, displaces somewhat the mean 

 position of these lines. The form of the arcs, and the radiating 

 character of the rays, not from the horizon but from near the 

 zenith, would seem to be due entirely to perspective effects. 

 The close concurrence between times of greatest auroral and 

 greatest sunspot frequency seems to establish some probable 

 cause and effect relationship between these two phenomena. 

 The infrequency of the displays of the past season is to be con- 

 sidered in connection with the fact that we are now near the 

 minimum period of the sun-spot cycle. I do not pretend to 

 understand, much less to explain the theories advanced along this 

 line, tho the picture of electrons in countless numbers hurtling 

 thru space and arranging themselves in mathematically beautiful 

 precision along the earth's magnetic lines, and all because of 

 some eruption on the sun, is fascinating enough. But, in the 

 little reading I have done on this subject, I have the feeling that 

 scientists are overlooking some possible closer relationships. 

 For example, is there any connection between aurorae and pre- 

 vailing weather conditions? My own observation is that the 

 displays only occur under certain conditions. Of course, a clear 

 sky is necessary for visibility; tho the lights may be seen at 

 times through breaks in the clouds, or even under high clouds. 

 But I do not recall ever having seen an aurora on a sultry night, 

 or just after a period of rainy weather, tho the sky is often ex- 

 ceptionally clear then. The displays do occur during local 

 thunderstorms, however. One of the finest sights I have seen 

 was in the autumn of 1920, when, with a bright moon shining 

 above, a heavy thimderstorm with vivid lightning was in progress 

 to the south, and a splendid showing of Northern Lights with 

 pronounced color effects could be seen in the North and West. 

 I have found it possible to predict with a considerable degree of 

 accuracy the near-future occurrence of the Lights, tho whether 



