Mr. Birt on a Paraselene witnessed May 6th, 1841. 51 



I first saw this interesting phaenomenon about a | past 1 1, 

 and as I continued to watch it, several appearances presented 

 themselves which (should they have been noticed by others) 

 may probably assist in determining some interesting particu- 

 lars relative to the clouds that were passing at the times of 

 observation, the area they extended over, etc. I therefore 

 subjoin the observations I made until the disappearance of the 

 paraselene ; 



And remain, my dear sir, yours very truly, 



W. R. Birt. 



Metropolitan Institution, May 7, 1841. 



1841. Mean Time estimated to the nearest minute. 



May 6. I l h 45 m . — The western illuminated portion nearly 

 disappeared, very faint, the semicircle still visible. 



May 6. 1 l h 49 m . — The western portion again visible, with 

 a streak of cloud extending from it to the east of the summit 

 of the semicircle. — The portion of the semicircle, where the 

 streak of cloud intersected it, was illuminated similar to the 

 three portions above mentioned. 



This streak of cloud passed over towards the south-east, the 

 eastern extremity of the semicircle being at the time much 

 more strongly illuminated than the western. 



May 6. 12 h 2 m . — A general cloudy appearance westward 

 of the semicircle, and the western extremity very distinct, ap- 

 proaching a decidedly circular form. 



May 6. 12 h 5 m . — The illumination of the eastern extre- 

 mity has nearly disappeared. 



May 6. 12 h 8 m . — Mars and Arcturus perfectly free from 

 clouds. 



May 6. 12 h 12 m . — A splendid meteor passed near the se- 

 micircle directly towards the horizon in the clear part of the 

 heavens. 



The clouds passing over appear to be curled cirri ; those 

 portions of them that intersect the semicircle in their passage 

 are more illuminated than the others. 



May 6. 12 h 15™. — The illuminated summit of the semi- 

 circle has entirely disappeared, owing to the passage of the 

 clouds towards the south-east ; the extremities of the semi- 

 circle still faintly visible. 



May 6. 12 h 18 m . — The semicircle obliterated, a small seg- 

 ment only visible to the east, with the eastern extremity very 

 faint. 



The degree of illumination was very variable, particularly 

 towards the end of the observations ; the western extremity 

 was just discernible when I left observing. 



E2 



