eee are ee ey 
Viewed as an electric discharge. — 31% 
_ as the voltaic are tends to revolve around the pole of a magnet, 
this “luminous atmosphere” or glow must do the same; and if 
the material composing the auroral arch be of the same nature 
its motion corresponding with that of the streamers. In the dis- 
play of August 28th, 1859, such was actually observed to be the 
case, the fragments composing the arch, as well as the streamers, 
having a rapid motion from east to west. 
The foregoing considerations seem to render it probable that 
the aurora is essentially an electric discharge (see fig. 4, I 
between the magnetic poles of the earth,—leaving the immediate 
Vicinity of the north magnetic pole in the form of clouds of elec- 
trified matter which float southward through the atmosphere a 
t 
a height of forty miles or more from the earth, sometimes to a 
to 1852,” p. 487, the observer at Lowville says, “The arc remaine thre 
quarters of an hour, its highest point being at first about 10° north of the — 
i j he o a 
southerly direction, and continued its progress until it descended as man} as 40° 
south of the zenith, it then was broken up into parallel pieces which m majesti- 
cally westward, and gradually diminished in magnitude and lustre, till at length 
every vestige of the arc disappeared.” : 
Tn mc nisi aoa Ss aibanb i far north that it is too distant from obser- 
Vers in this latitude to permit them to determine anything as to the motion of its 
