930 Transactions of the American Institute. 



that he had heard the noise, and that it always coincided with the 

 himinoiis jets." 



" Dr. Gisler, who for a long time dwelt in the north of Sweden, 

 remarked that the matter of aurora lorealis sometimes descends 

 so low that it touches the ground; at the summit of high mountains, 

 it produces upon the face of the traveler an effect analogous to that 

 of wind." Any one who has placed his face or a hand, near an 

 intensely charged prime conductor, cannot fail to understand the 

 nature of the effect here spoken of. 



" Dr. Gisler adds, that he has frequently heard the noise of aurora 

 and that it resembles a strong wind, or the whizzing that certain 

 chemical matters produce in the act of decomposition," 



If the elective discharges through tiie liaze are interstitial darting 

 from needle to needle, as they, undoubtedly are, we cannot doubt 

 that such crepitation would be observed by persons near enough to 

 hear it. 



Tde Odor of Ozone. 



The pungent odor spoken of as observed by some who have heard 

 the noise, goes ftir to strengtlien the evidences here cited. This odor 

 is undoubtedly that of ozone, which is evolved, as well in the infini- 

 tesimal discharges of aurora as in flashes of lightning ; it is represented 

 as identical with that observed at the discharge of a powerful leyden 

 jar, and is, without doubt from the same cause. 



In view of the foregoing evidence, it seems to me that there must 

 have been some fallacy in the parallaxes which have placed aurora 

 at the great heights of four, five and six hundred miles, for, at such 

 elevations, there is no appreciable atmosphere, or, at most, it is too 

 rare to sustain clouds or haze of any kind. 



Is it not probable that tlie appearance presented by a haze in a given 

 region may change, according to the point from which it is observed, 

 or, may it not present an aurora^t one point and be dark at another? 

 Might it not have been so in the case of Franklin and Kendall, above 

 quoted ? 



Arago held tliat to attempt to measure the height of an 

 aurora was as futile as to attempt to measure the height of a rain- 

 bow. It is indeed certain that, in some points of view, each 

 observer does see his own aurora lorealis as he sees his own 

 rainbow. 



