376 The Rev. A. Weld's Account of the Aurora Borealis 



The mean amount of vapour mixed with the air would have 

 produced water, if all had been precipitated at one time on the 

 surface of the earth, to the depth of 5' 5 inches. 



The mean weight of a cubic foot of air at the level of the 

 sea, under the mean pressure, temperature and humidity, 

 was 5293 grains. 



And these values for Cornwall and Devonshire were 4*8 

 grains ; 0'9 grain; 0'843 ; 6*0 inches ; and 530 grains respect- 

 ively. 



LVIII. Account of the Aurora Borealis as seen at Stonyhurst 

 Observatory, October 184-8. By the Rev. Alfred Weld, 

 B.A., of Stonyhurst College*, 



/"\N the evening of this day I was fortunate enough to witness 

 ^-^ the most magnificent display of aurora borealis which has 

 been known in this part of the country for many years. The 

 following are the principal features as they were noticed at the 

 Observatory of Stonyhurst. 



At about 6 h 45 m p.m. it was observed that the sky in the 

 N.E. was tinged with crimson, and at the same time an arc 

 of light was seen stretching from N.N.E. to a point about 

 the N.W. From this arc great numbers of faint rays were 

 emitted in both directions. By degrees the whole of that por- 

 tion of the heavens became filled with rays of light, which were 

 spread in confusion over the sky, some arising immediately 

 from the horizon, others having their origin at different alti- 

 tudes : none of these were remarkable for length or intensity 

 of light. In the meantime the red in the N.E. was increasing 

 to a brilliant crimson, remaining perfectly fixed, except that 

 it extended itself northward like a great cloud of fire, and 

 assumed a very magnificent appearance, while the streamers 

 and sheets of light between the N. and N.W. underwent 

 rapid changes, exhibiting now a somewhat irregular inverted 

 arch, and now wound into a wreath so as to enclose an almost 

 perfect circle. Shortly after seven the spectacle was very 

 grand; from N.E. to S.W. the whole sky, to the altitude of 

 30° or 40°, was filled with sheets and streamers of light, all 

 nearly steady (if we except a certain tremulous motion which 

 seemed to animate the whole mass), and chiefly of a brilliant 

 crimson hive. 



During this time the cloud of red light continued station- 

 ary in the N.E., in the constellation Auriga, the principal 



* Communicated by the Author. 



