IF ALLEY'S COMET 



1 1 



Halley's Comet in 1456 (according to Lubieniecki, Theatrum Cometicum). 



would be very promptly disposed of. Of course, all computers are not 

 like the late Professor Safford, who used to compute such an orbit in 

 one hour, but we should probably not find it necessary to search long 

 for one who would undertake to do the work in ten or twelve days. 

 But the method developed by Xewton seems now very cumbersome 

 and its application laborious. Tt was, moreover, so far from comple- 



■■'•J 



4 



r 



>f™) 





) 



Tailless Comet of 684 (Halley?) in the Pleiades (according to Lubieniecki, 



Theatrum Cometicum). 



tion that no means were found for computing the elliptic elements 

 of a periodic comet unless it had been observed at a second return. 

 The identification, therefore, depended on the similarity of the elements, 

 a very uncertain criterion, as we shall see. 



It is not at all improbable that if Halley had known more of the 

 chances of failure which beset this method of identification he would 

 hardly have ventured to predict another return of his comet. The step, 



Halley's Comet in 1066, after its emergence from the Sun's Rays 

 (according to Lubieniecki, Theatrum Cometicum 1. 



