58 RECORD OF AURORAL PHENOMENA. 



than in any other period of the lunation, and that the}* were most numerous between the third 

 quarter and the new moon. 



7. That the appearance of the Aurora was registered at Bear Lake, in 1S25-26, 343 times, without 

 any sound having been heard to attend its motions. 



8. The height of the Aurora was not determined by actual observation; but its having been seen, 

 on several occasions, to illuminate the under surface of some dense clouds, is conclusive that its 

 elevation could not have been very great. "When Dr. Richardson and Mr. Kendall made their 

 excursion on Bear Lake, in the spring of 1826, the former saw the Aurora very brilliant and 

 active, displaying the prismatic colors, in a cloudless sky (on the 23d of April); while Mr. 

 Kendall, who was watching at the time, by agreement, for its appearance, did not see any corus- 

 cation, though he was only twenty miles distant from Dr. Richardson. 



9. The gold-leaf electrometer, which was kept in the Observatory, was never affected by the 

 appearance of the Aurora. 



10. On four occasions, the coruscations of the Aurora were seen very distinctly before the daylight 

 had disappeared, and we often perceived the clouds in the daytime disposed in streams and 

 arches such as the Aurora assumes. 



The opinions I have ventured to advance above, are at variance with the conclusions drawn by 

 Captains Parry and Foster from their observations at Port Boweii ; those officers inferring that 

 the Aurora does not influence the motion of the needle. But the discrepancy may be perhaps 

 explained by the difference in activity and altitude of the Aurora at the two places. 



I have stated that the needle is most affected when the Aurora is very active and displays the 

 prismatic colors. Captains Parry and Foster have informed me that the Aurora seen at Port 

 Bowen was generally at a low altitude, without much motion in its parts, and never exhibiting 

 the vivid prismatic colors, or the rapid streams of light, which are so frequently recorded in our 

 registers of its appearance at Fort Enterprise and Fort Franklin. At both these places, we as 

 often tcitnessed the coruscations crossing the zenith as at any other altitude, and under such a 

 variety of forms, and in such rapid motion as to baffle description. 



From the difference in the appearance and activity of the Aurora at Port Bowen and Forts Enter- 

 prise and Franklin, an inference may be deduced that the parallel of 65° N. is more favorable for 

 observing this phenomenon, and its effect on the needle, than a higher northern latitude." — 2 

 Franklin, cxlv-cxlvii. 



N. B. — 1. Brilliant coruscations cause a deflection of the needle. 



2. Aurora most active when it emerges from a cloud near the earth. 



3. When the Aurora is very active, a haziness is very perceptible about the coruscations. 



4. The nearest end of the needle is drawn towards the point whence the motion of the 



Aurora proceeds. 



5. A low state of temperature is favorable for the production of active coruscations. 



Fort Franklin.— Lat. 65° 11' 5G" N. Long. 123° 12' 44" W. October 26, 1825. Frankijn. 



"An arch of 20° elevation, extending from W. N. W. to E. N. E. by the north. The motion of the 

 light rushed at the first from the former to the latter point, and then backwards and forwards, 

 and ultimately passed off to the southward. Needle stationary a few seconds. A beam shot 

 along the arch from west by north, to east. Beam from north, across the zenith, to south 

 horizon. Motion of light from W. N. W. along the arch. Motion from N. W. to N. E. at an 

 elevation of 8°. Beam from north to the zenith. Needle stationary, the Aurora having dis- 

 appeared. Interval of time — between lOh. 10m. and lOh. 30m. p. m. 



Remarks on the l^lh. — These coruscations were extremely brilliant, and in continual motion. 



The principal feature was a broad band of light that extended along the northern part of the sky, 

 from W. N. W. to E. N. E., at an elevation of 20°, from which beams of a less intense light were 

 frequently projected across the zenith from north to south, or in the contrary direction; and they 

 sometimes reached the opposite horizon before they disappeared. 



The band, as well as the beams, seemed to be composed of an infinite number of slender rays, 



