No. III.] 



Dr. RICHARDSON ON THE AURORA. 



627 



apparent convergence to the N.W. and S. E. points that has been described on 

 former occasions. 



Febuary 13th, 1821. At midnight, several layers of cirro-stratus in the 

 northern half of the sky, with clear blue intervals. A zone of light existed in 

 the north, its extremities bearing N. W. and E. N. E. It was composed of 

 parallel beams pointing to the southward, and having a quick lateral motion. 

 The eastern extremity of the zone was the most brilliant, and it sometimes rolled 

 back upon itself, producing various curtain-like appearances, during which mo- 

 tions it passed in front of the neighbouring clouds, and completely hid them. The 

 southern half of the sky was overspread with thin white clouds, through which 

 a few stars appeared. When these clouds passed over the face of the moon, 

 they produced a bur immediately around it, and a halo at the distance of 15°. 

 The northern edge of the halo was occasionally illuminated with the yellowish 

 red light of the Aurora, which gradually faded away into the white moon-light 

 reflected from the cloud. The zone in a short time broke up, and its parts 

 approached the zenith, often in their course whirling into a circular form, with 

 an extremely rapid motion. At those times the beams of light appeared to be 

 perpendicular to the horizon, and emitted various prismatic rays, of which 

 yellow and pale violet were the most conspicuous. Sometimes the violet 

 merely tipped the beams, at other times it appeared throughout their whole 

 length. When these beams were arrayed in the circular form, so as to form 

 -a ring, their length varied from 2° to 4°. The light appeared this evening to 

 the eye to be near the earth, a thin white haze evidently floating behind or 

 above it, in some places near the moon's situation in the sky. The needle, 

 by Mr. Franklin's observations, diverged very much to-night. 



A very short time after these observations were made, the whole sky was 

 overspread by a tolerably dense, uniform, hazy, white cloud, which hid the 

 stars, and considerably obscured the moon. The Aurora shot across this 

 cloud from N.N.W. to S.S.E., in the form of parallel arches, which emitted a 

 bright yellowish- white light. The arches were of short duration, and when 

 they disappeared, their site was observed to be occupied by the unaltered 

 stratum of cloud. 



March 8, 1821. At 6 p.m., before the daylight was gone, the Aurora appeared 

 in the S.E., stretching up towards the zenith. At seven, two faint arches crossed 

 the zenith. — Twilight. The Aurora was bright and copious all the evening. 



4 L 2 



