10§ REV. JAMES FARQUHARSON ON THE AURORA BOREALIS. 



house on foot, at half-past ten o'clock, I saw a fine display of the aurora bo- 

 realis, accompanied with peculiar circumstances, to be afterwards detailed, 

 which would scarcely leave a doubt respecting the elevation of the region which 

 it occupied above the surface of the earth. These peculiar circumstances ar- 

 rested my attention, and led me to observe eveiy thing in its appearance and 

 progress. When first seen it had already formed two distinct and separate 

 arches in the north and north-eastern parts of the heavens, the contimiity of 

 each of which was only interrupted by a few detached masses of low clouds, 

 coming, with a gentle breeze, slowly from the north, and brightly illuminated 

 by the moon. The most southerly arch approached within about 25° of the 

 zenith. It was abruptly terminated at its west extremity, about 35° above the 

 horizon ; as will be afterwards more particularly described in discussing the 

 question of the height above the surface of the earth. This west abrupt ex- 

 tremity was a little to the north of west. Its east extremity was near the ho- 

 rizon in north-east, nearly as I could judge at the time. The streamers at the 

 vertex of this arch were very short and compact, and parallel to the magnetic 

 meridian. Frgm this point, towards both extremities, the streamers gradually 

 increased in length, and being all directed to a point apparently 10° or 15° 

 south of the zenith, all formed angles with the general line of the arch, which 

 were more acute in proportion to the distance from the vertex. The arch might 

 be about 10° broad, and speedily moved southward, maintaining a parallelism 

 with its first position. Its lateral dimensions became gradually contracted. 

 The streamers near the zenith shortened into dense bundles, like sheaves of 

 light, parallel to the magnetic meridian, and consequently at right angles to 

 the general line of the arch ; and those towards the extremities gradually di- 

 minished the angles which they made with that line, and approached to a 

 parallelism with it. At length after reaching the zenith, the arch became 

 diminished in breadth to about 3° or 4°, and coincided in its whole extent with 

 the prime vertical to the magnetic meridian ; and the light at its vertex ex- 

 hibited a nebulous or mottled appearance, and that of the extremities of long 

 streamers or pencils of rays, now parallel to the arch itself. I had no oppor- 

 tunity, upon the present occasion, to witness the enlargement of the breadth 

 again, and the unfolding of the parallel streamers at the vertex, which I had 

 observed in former arches when they got considerably beyond the zenith ; for 



