40 THE CLIMATOLOGY OF THE UNITED STATES. 



lingered but a little while and the moon and sky then ap- 

 peared as clear as usual. 



A theory was then evolved and adopted to explain this 

 appearance. It was to the effect that owing to the ex- 

 tensive forest fires then raging to the north of New Eng- 

 land, a great quantity of smoke had drifted to the south 

 and east over the country, thus producing the yellow 

 light ; and in support of this theory it was stated that 

 many persons noticed an odor of smoke and that in New 

 Hampshire it was particularly strong. As no better expla- 

 nation was offered it was accepted generally. Nevertheless, 

 it would not satisfactorily stand a test. 



The ordinary ruddy glow of sunset is simply caused by 

 the way in which the rays of light penetrate the atmos- 

 phere which is apt to contain considerable moisture ; but 

 when we have to deal with a phenomenon like the Aurora 

 Borealis (or northern lights) we find we have a more com- 

 plicated subject to analyze. We can scarcely say that the 

 light is caused by the presence of gross foreign matter in 

 the air, unless we class magnetism and electricity as such. 

 This light at times appears in the form of a few streamers 

 or an arch of white light. At other times it will rise to the 

 zenith and even stretch over towards the south. Occasion- 

 ally, it spreads over a large part of the distance between 

 the east and the west, and at times it assumes a reddish 

 hue, and the flickering and darting motions of the stream- 

 ers or rays are very common. It has been noticed that a 

 brilliant displa}' of this kind often accompanies or follows a 

 sun storm, that is, a disturbance in the envelope of the 

 sun, such as may be witnessed in the development and ex- 

 pansion of a so-called sun spot. A change of weather or 

 of temperature is also looked for, after a display of north- 

 ern lights. This subject is little understood, yet we can 

 but feel that a bond of sympathy exists throughout the 



