Observations on Donati's Comet of 1858. 44'9 



On the evening of the 18th it was dim and near the horizon, 

 and required the aid of powerful telescopes to distinguish it, 

 although it was seen as late as the 22nd in some of the United 

 States Observatories south of us. On the 21st its N. P. D. was 

 118 ° 15', having passed over upwards of 106 ° in its path. At 

 •each observation a dark shade of light could be seen passing 

 from the body of the central nebulous mass, triangular in shape, 

 •as though the body of the comet projected a shadow on the 

 •surrounding coma. The direction of this shadow was upwards. 



From some recent calculations of Bruhns of Berlin, he is of 

 opinion that the period of its revolution round the sun exceeds 

 2,000 years. Loewy has "fixed its period of revolution at 2,494 

 years. 



The Chinese records make mention of a comet which ap- 

 peared 331 years before the Christian era, associated, as customary, 

 with the popular belief of wars and disasters, and corresponding 

 in date with the battle of Arbela. These records also make mention 

 of the appearance of remarkable comets both at an earlier and a 

 later date. 



Donati's comet seems to have surpassed the comet of 1811 both 

 in size and brightness ; the extreme length of its tail, according; 

 to Sir Wm. Herschell, was only 25 degrees, while that of Donati's 

 on the 10th of October was nearly 50 degrees in length. The 

 night of the 10th was peculiarly fitted for observation, and nothing 

 •could have exceeded the magnificent blaze of light that proceeded 

 from both the nucleus and tail. 



Its appearance, course, motion, and disappearance would tend 

 to the opinion that it is a distinct body from the comets of 1264 

 and 1556 ; so that the appearance of the body that excited so much 

 wonder at those periods of time, and which has occupied the 

 attention of mathematicians and astronomers up to the present 

 ■date, may yet be looked for. 



The superior advantages of observation that we now possess have 

 not been lost upon Donati's comet, and its place has been so 

 accurately laid down, that its reappearance cannot be mistaken ; 

 and the calculation of its orbit may in a measure tend to throw 

 some light on the perturbations that may influence all such-like 

 bodies. 



Several other comets were also visible during the year, but 

 -excited little attention owing to their small size. 



St. Martin, Isle Jesus, 1st Dec, 1858. 



D 



