of Halley, is the coincidence of the times of their appearances, as nearly as 

 historical records enable us to ascertain, with the epochs at which the comet 

 of Halley might have been expected to appear. That such evidence, however, 

 must needs be imperfect will be evident, if the frequency of cometary appear- 

 ances be considered ; and if it be remembered that hitherto we find no recorded 

 observations which could enable us to trace even with the rudest degree of 

 approximation the paths of those comets, the times of whose appearances raise 

 a presumption of their identity with that of Halley. We now, however, de- 

 scend to times in which more satisfactory evidence may be expected. 



In the year 1305, one of those in which the comet of Halley may have been 

 expected, a comet is recorded of remarkable appearance : Cometa horrendce 

 masnitudinis visus est circa ferias Pasckatis, quern secuta est pestileniia maxima. 

 Had the horrid appearance of this body alone been recorded, this description 

 might have passed without the charge of great exaggeration ; butVhen we find 

 the Great Plague connected with it as a consequence, it is impossible not to con- 

 clude that the comet was seen by its historians through the magnifying medium 

 of the calamity which followed it. Another appearance is recorded in the year 

 1380, unaccompanied by any other circumstance than its' mere date. This, 

 however, is in strict accordance with the ascertained period of Halley's 

 comet. 



We now arrive at the first appearance at which observations were taken, 

 possessing sufficient accuracy to enable subsequent investigators to determine 

 the path of the comet : and this is accordingly the first comet, the identity of 

 which with the comet of Halley can be said to be conclusively established. 

 In the year 1456, a comet is stated to have appeared, of " unheard-of magni- 

 tude ;" it was accompanied by a tail of extraordinary length, which extended 

 over sixty degrees (a third of the heavens), and continued to be seen during 

 the whole of the month of June. The influence which was attributed to this 

 appearance renders it probable that in the record there exists more or less of 

 exaggeration. It was considered as the celestial indication of the rapid sue- \ 

 cess of Mohammed II., who had taken Constantinople, and struck terror into \ 

 the whole Christian world. Pope Calixtus II. levelled the thunders of the ) 

 church against the enemies of his faith, terrestrial and celestial, and in the 

 same bull exorcised the Turks and the comets ; and in order that the memory 

 of this manifestation of his power should be for ever preserved, he ordained 

 that the bells of all the churches should be rung at midday a custom which is 

 preserved in those countries to our times. It must be admitted that, notwith- 

 standing the terrors of the church, the comet pursued its course with as much 

 ease and security as those with which Mohammed converted the church of St. 

 Sophia into his principal mosque. 



The extraordinary length and brilliancy which was ascribed to the tail upon 

 this occasion, have led astronomers to investigate the circumstances under 

 which its brightness and magnitude would be the greatest possible ; and, upon 

 tracing back the motion of the comet to the year 1456, it has been found that it 

 was then actually under the circumstances of position with respect to the 

 earth and sun most favorable to magnitude and splendor. So far, therefore 

 the results of astronomical calculation corroborate the records of history. 



The next return took place in the year 1531. Pierre Appian, who first as- 

 certained the fact that the tails of comets are usually turned from the sun, ex- 

 amined this comet, with a view to verify his statement, and to ascertain the 

 true direction of its tail. He made accordingly numerous observations upon 

 its position, which, though, compared with the present standard of accuracy, 

 they must be regarded as of a rude nature, were still sufficiently exact to enable 

 Halley to identify this comet with that observed by himself in 1682. 



