;3(J RECORD OF AURORAL PHENOMENA. 



In the first, I shall class those which are formed like rainbows or arches, in the earliest stage of 

 their appearance. 



They rise with their centres sometimes in the magnetic meridian, and sometimes several degrees to 

 the eastward or westward of it. 



The number visible at the same time seldom exceeds five, and is seldom limited to one. The 

 altitude of the lowest, when first seen, is never less than 4°. As they advance towards the 

 zenith, their centres (or the parts most elevated) preserve a course nearly in the magnetic 

 meridian or parallel to it. But the eastern and western extremities vary their respective dis- 

 tances, and the arches become irregularly broad streams in the zenith, each dividing the sky 

 into two unequal parts, but never crossing one another till they separate into parts. 



Those ai'ches which were bright at the horizon increase their brilliancy in the zenith, and dis- 

 cover the beams of which they are composed when the interior motion is rapid. 



This interior motion is a sudden glow, not proceeding from any visible concentration of matter, 

 but bursting out in several parts of the arch, as if an iguition of combustible matter had taken 

 place, and spreading itself rapidly towards each extremity." — 1 Franklin (Hood), 580. 



N. B. — Shapes of the Aurora at its entry into the horizon ; First Class. 



1. Those which are formed like rainbows or arches. 



2. Rise with their centres sometimes on magnetic meridian ; sometimes E. or W. of it. 



3. Number visible at same time seldom exceeds five ; seldom limited to one. 



4. Rise towards zenith, with their centres nearly in magnetic meridian. 



5. But the E. and W. extremities vary their respective distances. 



6. Arches bright at the horizon, increase in brilliancy in the zenith. 



" The second general class of Auroras are those which propagate themselves from different points of 

 the compass, between north and west, towards the opposite points; sometimes, also, originating 

 in the S. E. quarter, and extending themselves towards the N. W. 



They may be subdivided, like the former, into the distant arches, which pass to the southward without 

 much visible change in their appearance ; and those which discover beams, and separate at 

 intervals into wreaths, flashes, and irregular segments, exhibiting all the phenomena described 

 above. 



In explaining the mode by which the two general classes of Auroras are conducted into the horizon, 

 I shall call the motion of the arches (which is in a plane seldom deviating more than two points 

 from the magnetic meridian) the direct motion, and that by which the Auroras propagate them- 

 selves nearly at right angles to the magnetic meridian the lateral motion. 



Let us suppose a mass of Aurora to be modelled at its birth in a longitudinal form, crossing the 

 meridians at various angles, the whole to be impelled with a direct motion towards the magnetic 

 south, but the parts having differeut velocities, and each extremity continually removing itself, 

 by a lateral motion, from the centre, so as to increase the length of the mass. 



If the centre enter the northern horizon, it will appear like an arch, the real extremities being 

 invisible; and its direct motion will carry it to the southward in that form. 



But if one extremity first enter the horizon, it will extend itself, by its lateral motion, to the 

 opposite point, passing at the same time, by its direct motion, to the southward." — 1 Franklin 

 (Hood), 582. 



N. B. — Second General Class of Aurora. 



1. Those which propagate themselves from different points of the compass. 



2. Direct motion. 



3. Lateral motion. 



4. Longitudinal form. 



Fort Enterprise.— Lat. 64° 28' 24" N. Long. 113° C W. March 8, 1821. Hood. 



"On the 8th of March, 1821, at 5h. 30m. p. m., immediately after sunset, an arched Aurora was 

 visible, extending from N. W. to S. E. by S. This was the earliest period of the day at which 



