IO 



THE POPULAR SCIENCE MONTHLY 



Halley's Comet in 1066 on thh Bayedx Tapestry. 



eighteen years, for the purpose of improving the lunar theory, a problem 

 which had long occupied much of his attention. He had the satisfac- 

 tion of completing this eighteen-year task before his death, which oc- 

 curred in 1742, his age being eighty-five. 



Soon after the development of Newton's method, Halley set to work 

 with the application to comets' orbits. Certain terms were tabulated in 

 order to facilitate the application, but even with this aid Halley him- 

 self, who delighted in large undertakings, seems to have been greatly 

 impressed with the magnitude of this one. The undertaking consisted 

 in computing the parabolic orbits of all comets where sufficient data 

 existed for this purpose, but, although the appearance of some four 

 hundred of these bodies had been noted during historic times, only 

 twelve had been sufficiently observed to give much hope of success. To 

 this first twelve were afterwards added twelve more. The final re- 

 sults of this long investigation were not published until 1749, when 

 it appeared with the title, " Synopsis Astronomise Cometae." In these 

 days, with improved methods of attacking the problem, such a task 



Representations of Comets as Flaming Swoisps. 



