98 KANT'S UNIVERSAL NATURAL HISTORY 



on their way they become bent more and more from 

 the perpendicular line of falling by the incorporation of 

 other rapidly moving portions of matter; yet at the end 

 they remain comets if those regions of space in which 

 they have formed themselves, have become cleared and 

 empty, by the matter it contained falling into the sun or 

 being collected into separate masses. This is the cause 

 of the eccentricities of the planets increasing with their 

 distances from the sun, which also holds good of those 

 heavenly bodies that are called 'comets,' because they 

 exceed the planets in this respect. There are indeed 

 two exceptions which interrupt the law of the eccentricity 

 increasing with the distance from the sun, and these are 

 found in the two smallest planets of our system Mars 

 and Mercury. But with regard to the former, it is probably 

 the neighbourhood of the very large planet Jupiter which, 

 by attraction on its side, has robbed Mars of the particles 

 needed for its formation, and has left it only space to 

 increase in towards the sun, thereby causing an excess 

 of the central force and eccentricity. And as regards 

 Mercury, the nearest but also the most eccentric among 

 the planets, it is easy to perceive that because the sun 

 in its rotation comes far short of the velocity of Mercury, 

 the resistance which it offers to the matter in the space 

 surrounding it will not only deprive the nearest particles of 

 their central movement, but that this resistance may easily 

 extend to Mercury and will have thereby considerably 

 diminished the velocity of its revolution. 



The most distinctive mark of the comets is their 

 eccentricity. Their atmospheres and tails, which on their 

 great approach to the sun are spread out by its heat, are 

 only consequences of it, although in ages of ignorance, 



