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 



