ao JSdiJcettanea Curio fa. 



By comparing together the Accounts of the 

 Motions of thefe Comets, 'tis apparent, their 

 Orbits are difpos'd in no manner of Order ; 

 nor can they, as the Planets are, be compre- 

 hended within a Zodiac k y but move indiffe- 

 rently every Way, as well Retrograde as Di- 

 rect i from whence it is clear, they are not 

 carry'd about or mov'd in Cortices. Moreover, 

 the Difbances in their Periheliunfs are fome- 

 times greater, fometimes lefs which makes 

 me fufpecr, there may be a far greater Num- 

 ber of them, which moving in Regions more re- 

 mote from the Sun, become very obfcurej and 

 wanting Tails, pafs by us unfeen: 



Hitherto I have confider'd the Orbits of 

 Comets as exadly Parabolick \ upon which 

 Suppofition ft wou'd follow, that Comets be- 

 ing impell'd towards the Sun by a Centripetal 

 Force, defcend as from Spaces infinitely di- 

 stant, and by their Falls acquire fuch a Velocity, 

 as that they may again runoff into the remo- 

 telt Parts of the Univerfe, moving upwards 

 with fuch a perpetual Tendency, as never to 

 return again to the Sun. But fince they ap- 

 pear frequently enough, and fince none of them 

 can be found to move with an Hyperbolick 

 Motion, or a Motion fwifter than what the 

 a Comet might acquire by its Gravity to the 

 Sun, 'tis highly probable they rather move in 

 very Excentrick Orbits, and make their Re- 

 turns after long Periods of Time : For fo their 

 Number will be determinate, and, perhaps, 

 not fo very great. Befides, the Space between 

 the Sun and the fix'd Stars is fo immenfe, that 

 there is Room enough for a Comet to revolve, 

 tho' the Period of its Revolution be vaftly long. 



Nqw, 



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