NORTHERN LIGHTS— EVE l53 



charged particles will show so marked a tendency to proceed toward 

 the two main magnetic poles of the earth. 



It may very well be asked why it is claimed that the projectiles come 

 from the sun. The answer is that auroras, sunspots, and magnetic 

 storms all follow, over a long series of years, the same periodic vari- 

 ation of increase and decrease in number and intensity. This is the 

 well-known 11-year cycle. In recent years the variation of the effec- 

 tive frequency required for radio signals across the Atlantic has been 

 found to follow the same cycle. The general result is that we have 

 a twofold aspect of the sun. On the one hand, it must be regarded 

 as a variable star with an 11-year period. On the other hand, it is 

 endowed with such marvelous constancy that the main temperature 

 of the earth has continued between the freezing and boiling point of 

 water ever since life first appeared upon the earth many hundreds 

 of millions of years ago, with every prospect of its long continuance. 

 The sun converts some of its mass into radiation at the rate of 3 or 

 4 million tons a second, and yet plenty remains. This delicate balance 

 of temperature must be an unusual feat, and is a thing which, if it 

 had not happened, would be deemed impossible. In my young days 

 Sir George Stokes would have said, "Design !" Today many say, 

 "Chance !" Looking on the matter as fairly as I can, and not attach- 

 ing too much weight to my enormous veneration of Stokes, it still 

 seems to me that he was probably correct. This is a difficult question 

 which everyone must decide for himself, unless he prefers to sit on 

 the fence. 



AURORA AND THE WEATHER 



There is a popular belief that a change of weather follows the 

 Northern Lights — a change for the worse. There are many beliefs 

 also connecting the moon and the weather ; for if the moon is linked 

 with the tides, why not with the weather? A glance at a large scale 

 map will show that many various types of weather, good, bad, and 

 indifferent occur at any and the same time, at different places on the 

 whole face of the earth, whereas the phase of the moon is the same 

 for all. A somewhat similar statement may be made about an auroral 

 display, which often covers a large region and has to be responsible 

 for varied conditions. Besides, the aurora is 50 to 60 miles high, and 

 our weather is brewed in the lowest 10 miles, for the very liighest 

 cirrus clouds are rarely higher than 6 miles. There is, however, this 

 point to be remembered: Northern Lights are not seen in cloudy 

 weather, but only in clear. Hence it is much more probable that rain 

 or cloud will follow the aurora than the reverse, but it is probably 

 erroneous to state that the change was caused by the aurora. 



