COMETS. 1 1 3 



period of 575 years. Again, from 531 to 1106, leaves a second period of 575 years; 

 and from 1106 to 1680, a period of 574 years, which Newton supposed to be about its 

 periodic time. If this conjecture be correct, the comet is now winging its flight from 

 the sun far beyond the orbit of Uranus, and will not return from its long pilgrimage 

 to revisit the fountain of light till the year 2255. How vast the circuit ! How opposite 

 the circumstances of the two extreme points of the route the perihelion, in the 

 immediate neighbourhood of the solar glory the aphelion, at the probable distance of 

 1 3 thousand millions of miles from him ! At the far extremity, the sun, if observed 

 by a spectator, would appear simply as a point of light, and at the other extremity 

 the solar orb would be seen nearly filling the whole hemisphere. At t\\e first recorded 

 appearance of this comet, it was seen as a long-haired star in the skies of Rome 

 during the games which the youthful Augustus exhibited in honour of Venus and 

 his uncle, the assassinated Caesar; and while the inhabitants of the capital hailed the 

 object as the Julium Sidus, conveying aloft the soul of the dictator, his ambitious 

 successor secretly regarded it as a presage of his own glory, while apparently falling in 

 with the popular notion. Pliny has preserved to us his published memorial respecting 

 it, which ran as follows : "In those days during the solemnity of my games there was 

 seen a blazing star for seven days together, in that region of the sky which is under 

 the north star Septentriones : it arose about the eleventh hour of the day, bright and 

 clear, and was evidently seen in all lands : by that star it was signified that the soul 

 of Caesar was received among the divine powers of the immortal gods." At its second 

 exhibition, in the fifth year of Justinian, in the month of September, the comet was seen 

 during twenty days in the western heavens with a tail inclining towards the north. The 

 Byzantine writers applied to it the name of Lampadias, because of its resemblance to 

 a burning lamp. Its third visit is mentioned by the chroniclers, who describe it as 

 like the blaze of the sun, having an immense train. At its fourth return, there was 

 a cultivated science able to grapple with its phenomena, and divest them of a super- 

 natural character. Upon its fifth appearance, after more than three centuries and a half 

 from the present have elapsed, if the estimate of the periodic time be correct, Gibbon has 

 speculated upon its course and phase engaging the astronomers of some, future capital 

 in the Siberian or American wilderness. Calculating backwards the periodic time, 

 Whiston brought a return of this comet into coincidence with the era of the Deluge, of 

 which he conceived it to have been the agent. He broached likewise the presumptuous 

 fancy of lost spirits being incarcerated in this body, and hurried by it to the extremes 

 of perishing cold and devouring fire, as a part of their punishment. Such chimeras 

 deserve no serious notice. 



The first comet whose return was predicted and determined made its appearance in 

 our heavens in the year 1682, the year following that in which the preceding had va- 

 nished. Though far inferior in magnitude and splendour to its predecessor, it was a 

 considerable object, and has now become in consequence of its associations one of the 

 most interesting bodies of the system. It presented a tail extending through thirty 

 degrees of the hemisphere ; and while science watched its movements, the eye of the 

 populace rested upon its form without alarm, as the former had signally failed in causing 

 any direful catastrophe. The views of Newton who had spoken of the older bodies as 

 planets without tails, and of comets as a species of planets revolving about the sun in 

 very eccentric orbits, had arrested the attention of Halley ; and probably his remarkable 

 achievement was suggested by the following passage in the third book of the "Principia," 

 "I leave the transverse diameters and times of revolution to be determined by the 

 comparison of comets which return after long periods of time in the same orbits." Upon 

 this hint Halley commenced calculating the orbits of all the comets upon which definite 



