J28 0jr TWO CELESTIAL BODIES. 



can enter into a proper examination of the fubjecl, it will be 



necelTary to lay clown fome definition of the meaning we have 



hitherto affixed to the term planet. This cannot be difficult, 



_, . . „ tince we have feven patterns to acliuft our definition by. I 

 Cntenons of i i *• • • + i 



planets. mould, for in fiance, lay of planets, 



t. Magnitude, j • They are celeftial bodies, of ar certain very confiderable 



fize. 



*. Orbits nearly q. They move in not very excentric ellipfes round the fun. 



1* Nearly in the ^. The p' anes °* their orbits do not deviate many degrees 



pi. ecliptic from the plane of the earth's orbit. 



^Motion di " 4. Their motion is direcl. 



5. Satellites or 5. They may have fatellites, or rings. 



T 2 De l' r u 6. They have an atmofphere of confiderable extent, which 



6. Atmofpherr, 3 * ' . 



not extenfive. however bears hardly any fenfible proportion to their dia- 



7. Orbits con- mC f Crs . 



fiderab'v afun- ... . /-tiivn r 



«kr. ' 7. Their orbits are at certam confiderable diitances from 



Comparifonof each other. 



thefe tdot&t'. Now, if we may judge of thefe new ftars by our firft crite- 

 rion, which is their fize, we certainly cannot clafs them in the 

 lift of planets : for, to conclude from the meafures I have 

 j taken, Mercury, which is the fmalleft, if divided, would 



make up more than 1 35 thoufand fuch bodies as that of Pallas, 

 in bulk. 



In the fecond article, their motion, they agree perhaps fuf- 

 ficiently well. 



The third, which relates to the fituation of their orbits, 

 feems again to point out a confiderable difference. The geo- 

 centric latitude of Pallas, at prefent, is not lefs than between 

 17 and 18 degrees; and that of Ceres between 1.5 and 16; 

 whereas, that of the planets does not amount to one half of that 

 quantify. If bodies of this kind were to be admitted into the 

 order of planets, we fhould be obliged to give up the zodiac ; 

 for, by extending it to them, thouJd a few more of thefe ftars 

 bedifcovered, ftill farther and farther deviating from the path of 

 the earth, which is not unlikely, we might foon be obliged to 

 convert the whole firmament into zodiac ; that is to fay, we 

 mould have none left. 



In the fourth article, which points out the direction of the 

 motion, thefe ftars agree with the planets. 



(To be continued in our next. J 



