NORTHERN LIGHTS— EVE 149 



dark region where the observer stands.^ Those auroras which occur 

 wholly in a dark atmosphere range from 60 miles to 200 miles. 

 Thus the upper ionized atmosphere appears to expand by day and 

 shrink at night. Appleton has found similar results when measuring 

 the altitudes of those ionized reflecting regions which echo back wire- 

 less waves of suitable wave length. 



Notwithstanding these definite facts, and the further one that 

 Northern Lights appear behind distant mountains, there are many 

 who declare that they have seen an aurora close to the ground. An 

 engineer, with excellent judgment and good observational powers, 

 assured me that he had once seen personally some of his men walk 

 into an aurora ! A minister in Canada wrote to me that he was 

 drivmg a horse and buggy when a brilliant display of aurora ap- 

 peared near the ground close to his side. He declared that his horse 

 saw it too, for the animal first shied and then bolted. It is no good 

 telling these men that they could see no such thing. A probable but 

 not certain explanation is that a patch of mist close to the ground was 

 lit up by the vivid light of an aurora about 60 miles away.^ 



THE SOUND OF AURORAS 



Several observers, some of whom I have met personally, declare 

 that sometimes there occurs with an auroral display a sound, dis- 

 tinctly audible, that resembles the swish of a silk dress, or the noise of 

 a sword moved swiftly with the blade broadside to the air, or of wind 

 whistling in the rigging of a ship. A westerner declared that he was 

 prepared to take an oath (that he could hear the Northern Lights) 

 on a stack of Bibles as high as a church. This picturesque evidence 

 proves nothing, except that the man quite meant what he said. 

 Here is a letter, exactly as written, sent to me by a trapper in the 

 Province of Quebec. Such men live much in the open both by day 

 and by night, and they see much of nature : 



II a 6te donne ici une conference par un de vos professeurs dout je ne puis 

 me rapeler le nom, le subjet 6tais les Aurores-Boreales il disait done que c'est 

 impossible d'entendre le bruit des dit aurores. Je suis trapeur et peut predire 

 la temperature deux h trois jours d'advance par bien des signes quel vous ne 

 connaisser pas et quand des Aurores-Boreales se produisent sa agit sur la tem- 

 perature c'est par la place ici de dire sur quel cote du temps. 



Mais soyez certain aussi que certaine aurore produisent du bruit crepitement 

 faible c'est vrai et aussi comme un bruit de sole qu'une personne froisserait bien 

 9. vous. 



(Signed) Un Tbapeue. 



2 Science Rev., vol. 1, no. 3, p. 117, Feb. 1936. 



» See Low Auroras, by G. C. Simpson, Quart. Journ. Eoy. Meteor. Soc, vol. 59, pp. 185- 

 193, April 1933. 



