168 Results of a Meteorological Journal. [March, 



appeared round the sun, formed on thick lofty Cirri ; but they 

 gradually disappeared as these light clouds moved out of the 

 vicinity of the sun towards the East. 



Lunar Halo. — The most beautiful of the lunar halos appeared 

 on November 24, at nine P.M. ; it was formed on passing beds 

 of lofty attenuated Cirrocumulus from the N.W., and exhibited 

 four lively prismatic colours : its horizontal diameter, measured 

 by a sextant, was 45°, Capella, in the constellation Auriga, being 

 22° 30' from the moon's centre, and on the exterior edge of the 

 halo which measurement doubled gives 45°. Its periphery was 

 most perfect at midnight, when the moon's altitude was greatest; 

 for the perpendicular diameter of a lunar or solar halo, when 

 between the horizon and zenith, is always somewhat greater than 

 its horizontal diameter. Both solar and lunar halos are har- 

 bingers of falling weather ; as rain generally follows in 12 or 24 

 hours, and sometimes sooner, after their appearance, particularly 

 if the wind come in a westerly direction over the Atlantic Ocean. 



To discover a Solar Halo. — Accustom yourself to look closely 

 into the atmosphere, within a few degrees of the sun, when the 

 sunshine is rather faint, and no appearance of cloud near the sun 

 at the time. 



A lunar halo is more easily discovered, from the moonlight 

 being feeble, and less brilliant than the solar rays. 



Rainbcnv. — The widest and most perfect rainbow appeared 

 on October 12, at half-past four P. M. ; the diameter of its 

 exterior bow along the earth, as measured by the sextant, was 

 rather more than 100°, which is the widest we can possibly see. 



The lunar iris, or rainbow, appeared on August 25, at half- 

 past eight o'clock in the evening, for about ten minutes, on a 

 large Nimbus in the N.W., the moon being nearly at the full, 

 and shining brightly in the S.E. : the prismatic colours of this 

 rare phenomenon were distinctly seen, but they were consider- 

 ably fainter than those which constitute the solar bow. The 

 lunar iris is nearly of the same extent as the solar, and formed 

 in a similar manner ; namely, by the refraction of the moon's 

 rays in the drops of rain in the night. 



Aurora Borealis. — The first appearance of the Aurora Bo- 

 realis was from eight till ten P. M. on February 8 ; but as that 

 part of the northern hemisphere from the horizon to 70° in alti- 

 tude was almost overcast with Cirrostratus, its appearance here 

 was not very remarkable, except in the instance of a few of the 

 coloured coruscations that extended beyond the zenith south- 

 ward. The sky being partly clear in the north the following 

 evening, the lights were more distinctly seen ; they frequently 

 appeared in perpendicular columns, at other times arched, and 

 varied in colour, on account of the different degrees of rarefac- 

 tion of the air which they passed through. The last appearance 

 was on September 19, from half-past eight till nine P.M. between 



