472 Royal Astronojnical Society. 



manifestly in the same paragraph, that we may fairly question his 

 ability to describe accurately what he saw. Even in the case before 

 us there is some confusion, and M. Laugier has been obliged to 

 admit an alteration, which produces a contradiction in Giles's ac- 

 count, in order to reconcile the main part of his description with the 

 Chinese observations. 



The question stands thus : Halley's comet should have appeared 

 in all probability about 1301. We find in that year mention of a 

 comet, whose apparent path, according to the Chinese historians, is 

 well represented by the elements of Halley's comet : the only ob- 

 jection to the identity that can be advanced rests on an observation 

 of latitude by an European astronomer, or rather astrologer, whose 

 description of another comet has been shown to contain a manifest 

 contradiction, and who in the very case before us has committed 

 one pretty decided error. I am strongly inclined to recognise in 

 the first comet of 1301 Halley's famous star. 



It will readily be understood that I have not the slightest in- 

 tention to undervalue M. Laugier's investigation on this comet : 

 there can be no doubt, that if we admit the whole narration of Friar 

 Giles, his orbit must be retained, and in that case we must conclude 

 that the comet of Halley passed its perihelion about the year 1301 

 unobserved, or at least unrecorded. 



The preceding return of the comet took place, I think, in 1223^ 

 in the month of July, shortly before the death of Philip Augustus, 

 as French historians state. It was seen for eight days at the be- 

 ginning of July in the evening twilight. The Chinese have no 

 mention of this comet, and it unfortunately happens that European 

 chronicles give very vague accounts of it, so that we cannot come 

 to any definite conclusion respecting its identity with Halley's. 

 All that can be said is, that the few particulars we possess agree 

 perfectly well with the position of Halley's comet in the heavens 

 when the perihelion occurs in July, and that the comets of the pre- 

 ceding and following year, observed in China, appear to have had 

 very different elements. It is therefore most likely that our comet 

 was in perihelion in July 1223. 



In 1145 the return of the comet of Halley seems to me little less 

 than a matter of certainty. On carrying back the elements to that 

 epoch, and fixing the perihelion passage on April 19, the whole of 

 the particulars left us by the European and Chinese authors are 

 exactly represented. Its discovery in the morning twilight about 

 April 1 5, its increasing brilliancy towards the end of the month, the 

 disappearance about the first week in May, and rediscovery in the 

 evening sky in the north-west on May 14, and gradual fading away 

 in Hydra on the 9th of June, are fully explained, the positions 

 agreeing perfectly. 



The periods of revolution between 1145 and 1456 average 77|^ 

 years, and if we reckon backwards a like interval from 1145 we ar- 

 rive at the year 1067, about which epoch we may expect to recog- 

 nise the comet again. 



There is vague mention in several European chronicles of the ap- 



