Observations on Donates Comet of 1858. 447 



Mr. Dunthorpe of Cambridge, England, in comparing the elements 

 of the comets of 1264 and 1556, found them so similar, that the 

 two were considered by him as identical, and that it was a comet 

 whose period was about 292 years, making its re-appearance in 

 1818. 



Mr. Barber of Etwell, in following up these calculations, found 

 that Dunthorpe had not taken into account the perturbations 

 occasioned by Jupiter and Saturn, and he found that between the 

 years 1556 and 1592 their united attraction would diminish the 

 period of its appearance 263 days, but that between 1592 and 

 1806 it would be increased, by the action of Jupiter alone, no less 

 than 751 days, or more than two years. 



Babinet of Paris has also published his results, and found that 

 the orbits of the comets of the years 304, 685, 975, 1264 and 

 1556, have some appearances in common, and have always been 

 marked with an extraordinary display. 



Bomme of Middleburg has re-calculated their orbits, and says 

 that the re-appearance of the last may be expected in August 

 1858, with an uncertainty of two years. 



Hind of Bishop's Observatory, Regent's Park, has paid especial 

 attention to the orbits of the comets of 1264 and 1556, and, after 

 many intricate and careful calculations, taking into account the 

 perturbations caused by Jupiter, Saturn, and Neptune, has also 

 come to the conclusion that the comet of 1856 would probably 

 appear in August 1858, with an error of two years. 



The opinion of this eminent practical astronomer has often been 

 the subject of severe criticisms, owing to the misrepresentation of 

 what has been called his " predictions," which have in reality been 

 nothing more than opinions, and probabilities reduced from 

 deductions and calculations worked out by himself, upon the orbits 

 of these comets, which are bodies of a very uncertain nature. 



Hock of Leyden has recently raised some objection to the views 

 of Hind on the identity of the comets of 1264 and of 1556 ; but 

 Hind, in a letter written to me under the date of the 12th May, 

 1857, says : " I still maintain the opinion that I have so long held 

 respecting the identity of the comets of 1264 and 1556." 



The re-appearance of this remarkable, comet will throw much 

 light upon the perturbatory influences of those heavenly bodies, 

 which may be in proximity to its orbit, and it can now be scarcely 

 doubted that Donaii's comet of 1858 was not the expected comet 

 of 1556. 



