i2 THE POPULAR SCIENCE MONTHLY 



in any case, was a bold one but, fortunately for Halley's reputation and 

 for science, the result fully justified it. 



The same process has been tried in many cases besides this one, but 

 this seems to be the only instance where the prediction has been verified 

 by success. Gibbon gives us a very interesting instance of this method 

 of identification. 1 After referring to the remarks of Seneca, already 

 quoted, he continues : 



Time and science have justified the conjectures and predictions of the 

 Roman sage : the telescope has opened new worlds to the eyes of astronomers ; 

 and, in the narrow space of history and fable, one and the same comet is already 

 found to have revisited the earth in seven equal revolutions of 575 years. The 

 first, which ascends beyond the Christian era 1767 years, is coeval with Ogyges, 

 the father of Grecian antiquity. And this appearance explains the tradition 

 which Varro has preserved, that under his reign the planet Venus changed her 

 color, size, figure and course; a prodigy without example either in past or 

 succeeding ages. The second visit, in the year 1193, is darkly implied in the 

 fable of Electra, the seventh of the Pleids, who have been reduced to six since 

 the time of the Trojan war. That nymph, the wife of Dardanus was unable to 

 support the ruin of her country: she abandoned the dances of her sister orbs, 

 fled from the zodiac to the north pole, and obtained, from her dishevelled locks, 

 the name of comet. The third period expires in the year 618, a date that exactly 

 agrees with the tremendous comet of the Sibyl, and perhaps of Pliny, which 

 arose in the west two generations before the reign of Cyrus. The fourth appari- 

 tion, 44 years before the birth of Christ, is of all others the most splendid and 

 important. After the death of Caesar, a long-haired star was conspicuous to 

 Rome and to the nations, during the games which were exhibited by young 

 Octavian in honor of Venus and his uncle. The vulgar opinion that it conveyed 

 to heaven the divine soul of the dictator, was cherished and consecrated by the 

 piety of a statesman; while his secret superstition referred the comet to the 

 glory of his own times. The fifth visit has already been ascribed to the fifth 

 year of Justinian, which coincides with the 531st of the Christian era. And it 

 may deserve notice that in this, as in the preceding instance, the comet was 

 followed, though at a longer interval, by a remarkable paleness of the sun. 

 The sixth return, in the year 1106, is recorded by the chronicles of Europe and 

 China: and in the first fervor of the crusades, the Christians and Mahometans 

 might surmise, with equal reason, that it portended the destruction of the 

 infidels. The seventh phenomenon, of 1680, was presented to the eye of an 

 enlightened age. The philosophy of Bayle dispelled a prejudice which Milton's 

 muse had so recently adorned, that the comet from its " horrid hair shakes 

 pestilence and war." Its road in the heaven was observed with exquisite skill 

 by Flamsteed and Cassini : and the mathematical science of Bernoulli, Newton 

 and Halley, investigated the laws of its revolutions. At the eighth period, in 

 the year 2355, their calculations may perhaps be verified by the astronomers 

 of some future capital in the Siberian or American wilderness. 



In more recent times we have the remarkable group of bodies of 

 which the comets of 1668, 1843, 1882 are members; there are others, the 

 total number being probably very large. All of these bodies move 

 in orbits almost identical, almost grazing the surface of the sun at the 

 time of perihelion passage, and passing through millions of miles of the 



1 " Decline and Fall of the Roman Empire," Vol. IV., p. 289. 



