ON COMETS. 99 



beyond definite and narrow limits assignable by calcula- 

 tion. With comets it is far otherwise. They are wild 

 wanderers, and care nothing for beaten tracks. A comet 

 is just as likely to appear in any one region of the starry 

 heavens as in any other. They are no respecters of 

 boundaries. The first time a comet is seen, no one can 

 tell where it may next day be. The next observation 

 still leaves a great uncertainty as to its future course. 

 The third nails it. After three good observations, care- 

 fully made, of its place, we can thence foretell where it 

 will go. Meanwhile, such is the variety of which their 

 paths are susceptible, that for a very long time theii 

 movements were considered to be altogether capricious 

 and unaccountable creatures of chance governed by 

 no laws. Now the case is different. Most persons will 

 remember that the comet of 1858 passed on the 5th of 

 October of that year close to a very brilliant star, Arc- 

 turus, which shone through its tail at a very little distance* 

 from its root or outspring from the head. Well ! within 

 a very short time from the first appearance of that comet, 

 while yet it was but a faint object, it was known to cal- 

 culating persons that it would 'pass over Arcturus the 

 day the hour nay, almost the minute when the nucleus 

 of the comet would be closest to the star were predicted 

 and the prediction was exactly verified. How this 

 could happen I must now proceed to explain ; but before 

 I do so, I must premise that my hearers are not to be 

 startled if I use some words that are not familiar to many 

 of them, and ask for a little more of their attention than 

 if I were merely telling some amusing story. What I am 



