15-i G. F. Chamhers — Ilallei/s Comet. 



Art. XIV. — Ilalleifs Comet; by George F. Chambers, 



r.K.A.S.* 



This brochure, extracted almost verbatim from the author's 

 extended work, The Story of the Comets, published last year, 

 is intended to meet the large demand occasioned by the return 

 of Halley's comet for knowledge with regard to this comet and 

 such facts regarding comets in general as are necessary to make 

 the account of an individual comet intelligible in itself. 



It contains all that needs to be known by the general reader 

 of the past history of this comet and also of its present appear- 

 ance up to the time of its perihelion passage, shortly after 

 which this pamphlet was published. 



The purpose of the present article is to present for reference 

 in a form accessible to readers of this Journal a summary of 

 this pamphlet, supplemented by reports of the later period of 

 the comet's visibility sufficient to give a comprehensive view 

 of the knowledge acquired from the latest apparition of what 

 is generally considered to be, historically at least, the most 

 interesting of all comets. 



In anticipation of the return of the comet elaborate prepara- 

 tions were made by mathematical astronomers for its early 

 discovery. The labor of preparation was much increased by 

 the large perturbation by Jupiter soon after the perihelion of 

 1835. Nevertheless as early as 1864 Pontecoulant assigned a 

 date for the next perihelion which proved to be a close approx- 

 imation, and the final predictions of Cowell and Crommelin 

 published in January 1909 were but three days in error, the 

 actual date of perihelion being April 19. This result was con- 

 siderably closer than any obtained for the return in 1835. 



The competition for the earliest discovery of the comet by 

 photography was very keen and aroused much interest the world 

 over. The first announcement of its appearance was made by 

 Wolf from a plate taken September 11, 1909, at Heidelberg. 

 Soon after it was found to have been fixed on a plate taken at 

 Greenwich, Sept. 13, and some months later it was identified on 

 a plate taken by Keeling at Helwan in Egypt late in August. 

 Search had begun at Greenwich and Heidelberg as far back as 

 the early part of 1908, while an unsuccessful search by Dr. O. 

 J. Lee at the Yerkes Observatory in December, 1908, led him 

 to conclude that it was not then as bright as the 17th magnitude. 



The first visual observation of the comet was made at the 

 Lick Observatory with the 36-inch reflector on October 16. 



During November and December observations were numer- 

 ous at various observatories, but on the whole they wei*e neither 



* Oxford, Clarendon Press. New York, Henry Fronde, pp. 48. 



