REV. JAMES FARQUHARSON ON THE AURORA BOREALIS. 107 



this arch gradually faded and became extinct, about 10° or 12° southwards of 

 the zenith. 



The other arch of this evening was in its general outline parallel to the one 

 now described, but much lower in the heavens. It also ended abruptly at its 

 western extremity, on a point of the compass much nearer the north than the 

 termination of the other. Its vertex was on the magnetic meridian raised 

 about 26° or 30° above the horizon ; and its eastern extremity ended at the 

 horizon considerably to the eastward of north. In breadth it at first occupied 

 a space of probably 15° or 20°; but this could not be correctly estimated, as 

 its northern and southern edges were very irregular and variable, owing to the 

 incessant shortening and lengthening of the streamers of which it was com- 

 posed, which were nearly vertical, and therefore at right angles to the general 

 direction and line of the arch. This was its first appearance ; but it gradually 

 rose in the heavens, and became much enlarged both in length and breadth, 

 increasing the azimuth distance of its extremities from the north, as its vertex 

 rose higher in the heavens, but still remaining abruptly broken short at the 

 western extremity, and lengthening its vertical streamers till its middle part 

 reached an elevation of about 45°. In the mean time, however, the streamers 

 near the extremities were gradually changing the angle they made with the 

 line of the arch, constantly directing themselves, whatever position the arch 

 was in, to a point somewhat south of the zenith. After passing the elevation 

 of 45°, the streamers again gradually became shorter at the vertex ; and those 

 at the extremities going on at the same time to diminish their angle with the 

 line of the arch, the breadth of that became at all points gradually less. This 

 order of appearances went on till this arch had attained nearly the first position 

 and appearance of the one first described, when it rather suddenly became ex- 

 tinct about fifteen minutes after the other had disappeared. 



A luminous space near the north point of the magnetic meridian, appeared 

 at this time to promise the formation of a third arch, beginning to show a few 

 streamers ; but it soon gradually faded. 



On the evening of the 9th of September, 1827, at 11 o'clock, I witnessed a 

 very brilliant, and, with the exception of the one last described, the most in- 

 structive aurora borealis which it has fallen to my lot to observe. When first 

 seen, a bright arch of light of various width, and jagged at its edges, stretched 



p2 



