ON COMETS. 109 



the rein here and a Httle relaxation there, as they ca- 

 reered round and round, would suffice perhaps to keep 

 them regular, and guide them in their graceful and 

 smooth evolutions. But here we had a stranger from 

 afar from out beyond the extremest limits of our sys- 

 tem dashing in, scorning all their conventions, cutting 

 across all their orbits, and rushing like some wild infu- 

 riated thing close up to the central sun, and steering 

 short round it in a sharp and violent curve with a speed 

 (for such it w^as) of 1,200,000 miles an hour at the 

 turning point, and then going off as if curbed by the 

 guidance of a firm and steady leading rein, held by a 

 powerful hand, in a path exactly similar to that of its 

 arrival, with perfect regularity and beautiful precision ; 

 in conformity to a rule which required not the smallest 

 alteration in its wording to make it applicable to sucli 

 a case. If anything could carry conviction to men's 

 minds of the truth of a theory, it was this. And it did 

 so. I believe that Newton's explanation of the motions 

 of comets, so exemplified^ was that w^iich stamped his 

 discoveries in the minds of men with the impress of 

 reality beyond all other things. 



(19.) This comet was perhaps the most magnificent ever 

 seen. It appeared from November 1680 to March 1681. 

 In its approach to the sun it was not very bright, but 

 began to throw out a tail when about as far from the sun 

 as the earth. It passed its perihelion on December 8 

 and when nearest was only one- sixth jjart of the sun's 

 diameter from his surface one fifty-fourth part of an inch 

 on the conventional scale of our imaginary figure, and at 



