THE GREAT COMET OF 1843. 131 



probable orbit to be an ellipse of over 500 years. We 

 seem, obliged then, entirely to reject any short period, as 

 20 or 30 years, and there seems but slight probability 

 that this comet is identical with that of 1668. It is doubt- 

 ful whether the period of this comet can be certainly de- 

 termined until it has been again observed on its return to 

 the sun. 



The following circumstances invest the comet of 1843 

 with peculiar interest. 



1. Its small perihelion distance ; being as small as that 

 of any comet whose orbit has been computed, and nearly 

 as small as is physically possible. 



And 2. Its prodigious length of tail; being equal to 

 that of any comet hitherto observed. 



