284 PHYSICAL SCIENCE BK. vn 



two blends in one, producing the appearance of a 

 more elongated star. This happens not merely 

 when star touches star, but even when one ap- 

 proaches another. The space between the two 

 is in that case lit up by both, and seems aflame, 

 producing the trail of fire. 



XII 



1 OUR first answer to this theory is that the number 

 of moving stars (planets) is fixed. It is quite usual 

 for them and comets to appear at the same time ; 

 whence it is manifest that the comet is not due 

 to the conjunction of planets, but is a distinctive in- 

 dependent star. Besides, it is a matter of frequent 

 occurrence for a star to come under the orbit of 

 a more elevated star. Saturn, for example, is 

 sometimes above Jupiter ; Mars looks down in 



2 a straight line on Venus or Mercury. But yet 

 no comet is formed from this movement whereby 

 the one planet approaches the other. Were it 

 otherwise, there would be a comet every year, for 

 every year there are planets in the same constella- 

 tion. Again, if the approach of star to star pro- 

 duced a comet, the latter would cease to be in a 

 moment. The transit of stars takes place with 

 the utmost rapidity, thence all eclipse of heavenly 

 bodies is of brief duration ; by the same motion 

 they are as swiftly separated as they were brought 



3 together. The sun and the moon, as we see, part 

 company within a brief space after the eclipse has 

 begun. How much swifter must be the separation 

 of stars, which are so much smaller? Yet comets 

 last for six months at a time, which would not 



