y 



• 



t 



y 



138 



Gannett's Account of an Aurora Borealis. 



the distance of 



enomenon from 



he 



sav 



miflit be computed. He however cannot admit the sup 



position, 

 phenoinei 



he can 



the 



onclusion 



uld 



b 



that 



the 



I have been distant at least 



1 



2¥ 



of the 



diameter of the earth, which is too great an altitude *to 

 believe. He had previously offered a conjecture, respect- 



the production of the zone, viz. from icy particles 



mg 



swimming in the air, and of such a figure, 



as to 'exhibit a 



great zone by the reflection and refraction' of the light of the 

 aurora, almost in the same manner as the drops of rain pro- 

 duce the appearance of the rainbow. "Whether this hypo- 

 thesis, incompatible with the foreraentioned conclusion, on 



of the rarity of the atinospl 



at that height 



which renders it incapable of sustaining particles, whose spe- 

 cifick gravity should be such as to cause the reflections and 

 refractions necessary for such a phenomenon, might Bot 



b 



his judgment, may be questioned. He* m 



two 



fr 



the 



and south 



meetins: in the 



d 



immediately afterwards parting, d 



o 



back 



and frequen 



ipeating those motions. These arches must 



be supposed to originate from the same cause with that of 

 the zone J but whether their motions agree with the cause 

 conjectured, every one will judge. 



Mr. Professor Greenwood, in an account of an aurora 

 borealis, observed by him 



that this meteor has been observed 



at Cambridge 



N 



in 1730, affirm 



England 



dif 



ferent times, ever since its first plantation ; which is contra- 



• 



ry to the commonly received 

 date in this part of the 



opinion, that 



1 



of model 



orld 



Its appearance howeve 



was 



• 



